All practice questions

Question 13821Question →

Match each of the following Nigerian mineral or energy resources on the left with its primary deposit locality or operational power facility site on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Sub-bituminous coal matches with Enugu (Enugu State); Gas-fired thermal electricity plant matches with Egbin (Lagos State); Limestone for cement production matches with Nkalagu (Ebonyi State); Tin and columbite deposits match with Bukuru (Plateau State).

Each mineral or energy installation is accurately linked to its principal production locality: Sub-bituminous coal to Enugu, Gas-fired thermal electricity plant to Egbin, Limestone to Nkalagu, and Tin/Columbite to Bukuru.

Step-by-Step Solution

1

Identify the geographical occurrence of solid energy and metallic mineral resources.

Sub-bituminous coal is tied to the Cretaceous rocks of Enugu, while tin and columbite ores occur in the Younger Granites of Bukuru on the Jos Plateau.

Geological rock formations determine the specific location of fossil fuels and metallic mineral deposits across Nigeria.

2

Identify industrial sedimentary minerals and thermal energy infrastructure locations.

Limestone beds at Nkalagu supply cement manufacturing plants, while natural gas pipelines supply the Egbin thermal power station.

Commercial mineral exploitation depends on large sedimentary limestone reserves, and thermal power stations are sited near gas supply networks and major consumer centers.

Key Concept

Geographical distribution of major mineral deposits and energy stations in Nigeria

Question 13822Question →

Match each major African trade-supporting railway corridor listed on the left with its corresponding primary economic trade function and regional geographical link on the right.

Click a left item, then click its matching right item

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Answer

TAZARA Railway matches with the link between Zambia and Dar es Salaam; Benguela Railway matches with the corridor from Katanga/Angola to Lobito; Dakar–Niger Railway matches with the trade connection between Dakar and Bamako; Mauritania Desert Railway matches with the iron ore transport from Zouérat to Nouadhibou.

Each rail corridor is accurately linked to its geographical hinterland and trade objective: TAZARA provides an Indian Ocean route for Zambian copper to Dar es Salaam; Benguela links the Katanga mining region across Angola to Lobito port; Dakar–Niger provides ocean access to landlocked Bamako; and the Mauritania Desert line carries iron ore from Zouérat to the port of Nouadhibou.

Step-by-Step Solution

1

Identify the primary economic rationale and terminals of the TAZARA Railway.

TAZARA connects Kapiri Mposhi in landlocked Zambia to Dar es Salaam in Tanzania, serving Zambia's copper exports.

Zambia required a trade corridor independent of southern routes prior to regional political transitions.

2

Identify the territorial path and ocean port connected by the Benguela Railway.

Benguela runs through Angola to Lobito port, linking Katanga's mining sector in DRC to the Atlantic Ocean.

Lobito serves as the key Atlantic gateway for Central/Southern African mineral trade.

3

Examine West African landlocked transit corridors, specifically Senegal and Mali.

The Dakar–Niger line links Dakar on the Atlantic coast to Bamako on the Niger River.

It offers essential transit trade for landlocked Mali across Senegalese territory.

4

Determine the dedicated mineral extraction line in North-West Africa (Mauritania).

The Mauritania Desert Railway carries iron ore from Zouérat to the port of Nouadhibou.

Bulk mineral export requires specialized heavy-rail infrastructure to reach coastal shipping hubs.

Key Concept

African Rail Transport Corridors and Trade Hinterlands

Question 13823Question →

Match each Geographic Information System (GIS) spatial analysis function on the left with its corresponding real-world geographic application on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Buffering pairs with creating a 500-meter protection zone; Overlay Analysis pairs with combining land use, slope, and soil maps for landfill site selection; Network Analysis pairs with finding the most efficient travel route through an urban road system; and Spatial Interpolation pairs with estimating temperature values at unmeasured locations.

Each spatial function maps directly to its operational definition: Buffering establishes distance boundaries (500-meter river zone); Overlay Analysis combines multiple layer criteria (landfill site selection); Network Analysis optimizes routing over line networks (emergency response travel); and Spatial Interpolation estimates continuous surface fields from point measurements (weather station interpolation).

Step-by-Step Solution

1

Identify the core operation of Buffering

Buffering involves creating a perimeter zone of defined distance around points, lines, or polygons, matching the creation of a 500-meter protection zone around a river.

Proximity analysis functions establish distance thresholds around spatial objects.

2

Identify the core operation of Overlay Analysis

Overlay analysis superimposes multiple thematic maps (slope, land use, soil) to solve multi-criteria suitability problems like landfill siting.

Spatially combining vector or raster layers enables multi-layered evaluation.

3

Identify the core operation of Network Analysis

Network analysis relies on interconnected linear paths to model flow, impedance, and optimal paths, matching emergency vehicle route selection.

Transportation and routing problems require topological network structures.

4

Identify the core operation of Spatial Interpolation

Spatial interpolation predicts values at unknown locations from known point samples, matching temperature estimation from surrounding weather stations.

Continuous atmospheric or environmental surfaces are modeled from point measurements.

Key Concept

GIS Spatial Analysis Functions

Question 13824Question →

A narrow beam of cathode rays is produced by accelerating electrons from rest through an unknown potential difference $V$ . The beam then enters a region containing mutually perpendicular uniform electric and magnetic fields of magnitudes $1.2 \times 10^4\text{ V/m}$ and $3.0 \times 10^{-3}\text{ T}$ , respectively. If the cathode rays pass through the crossed fields completely undeflected, what is the value of the accelerating potential difference $V$ ? [Take electron charge $e = 1.6 \times 10^{-19}\text{ C}$ and electron mass $m = 9.0 \times 10^{-31}\text{ kg}$ ]

45\text{ V}

90\text{ V}

180\text{ V}

7.2 \times 10^{-18}\text{ V}

Show answer & explanation

Answer: $45\text{ V}$

Answer

The accelerating potential difference

V

is

45\text{ V}

.

For cathode rays passing undeflected through crossed fields, the electric force equals the magnetic force (

eE = evB

), giving speed

v = E/B = 4.0 \times 10^6\text{ m/s}

. The work done by the electric field during acceleration from rest equals the kinetic energy:

eV = \frac{1}{2}mv^2

. Rearranging for

V

yields

V = \frac{m v^2}{2e} = \frac{(9.0 \times 10^{-31}) (4.0 \times 10^6)^2}{2 \times (1.6 \times 10^{-19})} = 45\text{ V}

. Therefore, the option stating

45\text{ V}

is correct.

Step-by-Step Solution

1

Calculate the velocity

v

of the cathode ray electrons using the undeflected condition in crossed fields

v = \frac{E}{B} = \frac{1.2 \times 10^4\text{ V/m}}{3.0 \times 10^{-3}\text{ T}} = 4.0 \times 10^6\text{ m/s}

When cathode rays pass undeflected through perpendicular electric and magnetic fields, the electric force

F_e = eE

balances the magnetic force

F_b = evB

.

2

Relate the kinetic energy gained by the electrons to the accelerating potential difference

V

e V = \frac{1}{2} m v^2 \implies V = \frac{m v^2}{2 e}

The work done by the accelerating potential difference equals the final kinetic energy of the electrons starting from rest.

3

Substitute the known physical quantities into the potential difference formula

V = \frac{(9.0 \times 10^{-31}\text{ kg}) \times (4.0 \times 10^6\text{ m/s})^2}{2 \times (1.6 \times 10^{-19}\text{ C})} = \frac{9.0 \times 10^{-31} \times 1.6 \times 10^{13}}{3.2 \times 10^{-19}} = 45\text{ V}

Evaluating the expression yields the required voltage

V = 45\text{ V}

.

Key Concept

Deflection of Cathode Rays in Crossed Fields and Energy Conversion in Cathode Ray Tubes

Question 13825Question →

Match each drainage pattern type with its corresponding underlying geological or structural control.

Click a left item, then click its matching right item

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Answer

Dendritic pattern matches Uniformly resistant horizontal rock strata; Trellis pattern matches Folded topography with alternating parallel belts of hard and soft rocks; Radial pattern matches Central elevated dome, volcanic cone, or isolated peak; Centripetal pattern matches Enclosed inland basin, crater lake, or structural depression.

Each drainage pattern forms under specific geological conditions: uniform rock lithology allows random tree-like branching (dendritic), folded alternating hard/soft rocks force right-angle junctions along strike valleys (trellis), central high points divert water outward in all directions (radial), and central low depressions gather surrounding drainage inward (centripetal).

Step-by-Step Solution

1

Identify the geometrical characteristics of each drainage network

Tree-like branching (Dendritic), rectangular grid-like joining (Trellis), radiating outwards (Radial), and converging inwards (Centripetal).

Channel alignment is determined directly by geological controls and landforms.

2

Relate stream geometry to underlying rock structure and topography

Uniform resistance creates dendritic, folded structures yield trellis, high peaks create radial, and central depressions yield centripetal flow.

Subsurface rock hardness and surface slope dictate drainage network pattern formation.

Key Concept

Geological and structural controls on drainage patterns

Question 13826Question →

A cartographer is tasked with displaying population density across different administrative districts in a state by applying varying intensities of shading, where darker shades represent higher densities. Which statistical mapping technique is being described, and what is a primary cartographic limitation of this method?

Isopleth map, which inverts the numerical scale ratio when plotting continuous lines of equal value across administrative boundaries.

Choropleth map, which falsely assumes a uniform distribution of the phenomenon throughout each administrative unit.

Proportional symbol map, which incorrectly assumes that doubling the map's linear scale doubles the represented surface area.

Flow map, which misattributes depositional statistics to upper course geographical regions.

Show answer & explanation

Answer: Choropleth map, which falsely assumes a uniform distribution of the phenomenon throughout each administrative unit.

Answer

The correct mapping technique is a choropleth map, whose primary limitation is creating an illusion of uniform population distribution across the entire administrative unit.

A choropleth map uses tonal shading or graduated colors applied to specific boundary units (such as states or districts) to display average values or densities. A major limitation of this technique is the false assumption that population density is evenly distributed across the entire area inside each boundary.

Step-by-Step Solution

1

Identify the mapping technique based on the spatial data display method.

The technique using varying shades or patterns applied within pre-defined administrative boundaries to show density or average values is a choropleth map.

Choropleth mapping relies on quantitative areal data aggregated by spatial units such as states or districts.

2

Analyze the cartographic limitations of choropleth maps.

Choropleth shading covers entire administrative zones evenly, giving the false impression that values are uniform throughout each zone.

Administrative boundaries rarely align with natural transitions in population density or spatial phenomena.

Key Concept

Choropleth Mapping and Spatial Data Generalization

Question 13827Question →

A Vernier caliper with a least count of $0.01\text{ cm}$ is used to measure the internal diameter of a cylindrical pipe. When the jaws are fully closed without any object between them, the zero mark of the Vernier scale lies to the right of the zero mark on the main scale, and the $3\text{rd}$ Vernier division coincides with a main scale division. During measurement, the main scale reads $2.40\text{ cm}$ and the $6\text{th}$ Vernier division coincides with a main scale mark. What is the corrected internal diameter of the pipe?

2.43\text{ cm}

2.46\text{ cm}

2.49\text{ cm}

2.37\text{ cm}

Show answer & explanation

Answer: $2.43\text{ cm}$

Answer

The corrected internal diameter of the pipe is

2.43\text{ cm}

.

The Vernier caliper has a positive zero error because the zero mark on the Vernier scale lies to the right of the zero mark on the main scale when closed. The magnitude of this error is

3 \times 0.01\text{ cm} = +0.03\text{ cm}

. The observed reading is

2.40\text{ cm} + (6 \times 0.01\text{ cm}) = 2.46\text{ cm}

. Subtracting the zero error from the observed reading yields

\text{Corrected reading} = 2.46\text{ cm} - 0.03\text{ cm} = 2.43\text{ cm}

.

Step-by-Step Solution

1

Determine the zero error of the Vernier caliper.

Zero error

= + (3 \times 0.01\text{ cm}) = +0.03\text{ cm}

.

Since the zero of the Vernier scale lies to the right of the main scale zero mark, the instrument has a positive zero error.

2

Calculate the uncorrected (observed) reading.

\text{Observed reading} = 2.40\text{ cm} + (6 \times 0.01\text{ cm}) = 2.46\text{ cm}$.

The observed reading is the sum of the main scale reading and the Vernier scale coincidence value.

3

Apply the zero error correction formula.

\text{Corrected reading} = 2.46\text{ cm} - (+0.03\text{ cm}) = 2.43\text{ cm}$.

Corrected reading is given by subtracting the zero error (including its sign) from the observed reading.

Key Concept

Zero Error Correction in Length Measurement Instruments

Question 13828Question →

Match each domestic payment instrument used in home trade with its corresponding operational characteristic or function.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Credit Transfer matches with single banking instruction to pay multiple creditors; Standing Order matches with regular fixed payment instruction; Bank Draft matches with cheque drawn by a bank guaranteeing payment; Postal Order matches with prepaid instrument sold in fixed denominations.

Each instrument is correctly matched with its core defining operational feature: Credit Transfer enables single-instruction bulk creditor payments, Standing Order automates fixed recurring payments, Bank Draft provides guaranteed funds drawn on the bank itself, and Postal Order provides pre-denominated postal remittances.

Step-by-Step Solution

1

Identify the payment mechanisms used for bulk or multiple payments

Credit transfer enables a debtor to instruct their bank to distribute funds to several creditors at once.

It eliminates the need to issue individual cheques for each creditor.

2

Identify automated recurring fixed payment instructions

Standing order is an instruction to pay a set amount periodically.

It automates routine payments such as rent or club subscriptions.

3

Identify bank-guaranteed instruments

Bank draft is drawn directly by a bank on its own funds.

Because funds are debited immediately upon issuance, receiver default risk is eliminated.

4

Identify post office remittance methods

Postal orders are sold in fixed face values by the postal system.

They provide a secure method to send small amounts when banking facilities are unavailable.

Key Concept

Characteristics and functions of domestic payment instruments in home trade

Estimated Time:1m 30s

Question 13829Question →

Which of the following thermal power stations in Nigeria relies primarily on natural gas and is located in the Niger Delta region?

Afam Power Station

Oji River Power Station

Shiroro Power Station

Kainji Power Station

Show answer & explanation

Answer: Afam Power Station

Answer

Afam Power Station is a natural gas-powered thermal station located in Rivers State in the Niger Delta.

Afam Power Station in Rivers State is situated directly in the Niger Delta oil and gas belt, using abundant local natural gas supplies for thermal electricity generation.

Step-by-Step Solution

1

Identify the primary fuel source associated with Niger Delta thermal power generation.

The Niger Delta is rich in crude oil and natural gas deposits, powering gas thermal stations like Afam, Ughelli, and Sapele.

Geological alignment pairs natural gas extraction in oilfields directly with nearby thermal power plants.

2

Distinguish between thermal (gas/coal) and hydroelectric power stations in Nigeria.

Hydroelectric stations (Kainji, Jebba, Shiroro) are located on major rivers in central Nigeria, while coal-fired generation (Oji River) relied on sub-bituminous coal from Enugu.

Excludes hydro stations located in Niger State and coal stations in Enugu State.

Key Concept

Spatial Distribution of Energy Generating Facilities in Nigeria

Estimated Time:1m 0s

Question 13830Question →

Which of the following correctly pairs each risk management concept in List A with its corresponding operational description in List B?

Click a left item, then click its matching right item

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Answer

Underwriting matches the assessment and pricing of risk; Reinsurance matches a primary insurer transferring risk to another insurer; Co-insurance matches multiple insurers entering direct contracts with the policyholder; Retrocession matches a reinsurer ceding risk to another reinsurer.

Underwriting is the evaluation and pricing of risk. Reinsurance is risk shifting from a direct insurer to a reinsurer without insured involvement. Co-insurance is joint direct coverage between the policyholder and multiple insurers. Retrocession is reinsurance for reinsurers.

Step-by-Step Solution

1

Identify the risk evaluation and pricing mechanism.

Underwriting corresponds to assessing, selecting, classifying, and pricing risks prior to issuing cover.

Underwriting is the core diagnostic function performed by insurers before contract formation.

2

Differentiate between risk transfers involving the insured versus those restricted to insurers.

Co-insurance involves direct contractual relationships between the policyholder and multiple insurers, whereas Reinsurance is a secondary contract purely between the primary insurer and a reinsurer.

Reinsurance maintains no contractual relationship (privity of contract) with the original insured, while Co-insurance creates direct liability for each insurer to the insured.

3

Define the secondary transfer of liability within the reinsurance market.

Retrocession matches the process of a reinsurer spreading its accepted risk to another reinsurer.

Retrocession functions as insurance for reinsurance companies to prevent excessive concentration of loss.

Key Concept

Operational distinctions between Reinsurance, Co-insurance, Underwriting, and Retrocession

Question 13831Question →

In Mediterranean climatic regions, vegetation must endure intense summer droughts accompanied by mild, wet winters. Which of the following features is a primary characteristic adaptation of plants native to this biome?

Thick, hard, waxy leaves designed to minimize water loss through transpiration

Broad, thin leaves that are shed completely during winter months to withstand extreme sub-zero temperatures

Shallow spreading root systems with large buttress roots supporting a dense three-tiered canopy

Needle-shaped leaves with high resin content growing on shallow acidic podzol soil profiles

Show answer & explanation

Answer: Thick, hard, waxy leaves designed to minimize water loss through transpiration

Answer

Thick, hard, waxy leaves designed to minimize water loss through transpiration.

Mediterranean vegetation (sclerophyllous scrub such as chaparral, maquis, and garrigue) features small, thick, leather-like leaves with waxy cuticles to reduce moisture loss via transpiration during the dry, hot summer months.

Step-by-Step Solution

1

Analyze the climatic constraints of the Mediterranean biome

Recognize that the defining stress factor of this climate is a distinct hot, dry summer paired with mild, moist winters.

Plant adaptations directly mirror the environmental stress imposed by regional climatic seasonality.

2

Identify plant morphological strategies suited for summer drought stress

Vegetation adopts sclerophyllous characteristics—small, tough, waxy leaves, thick bark, and extensive root networks to limit transpiration and reach subterranean water stores.

Minimizing transpiration loss is crucial when water availability drops during the warmest period of the year.

Key Concept

Mediterranean Sclerophyllous Vegetation Adaptations

Estimated Time:1m 0s

Question 13832Question →

A stationary object of mass $5.0\text{ kg}$ explodes into two fragments of masses $2.0\text{ kg}$ and $3.0\text{ kg}$ . If the $2.0\text{ kg}$ fragment moves due east at a velocity of $15\text{ m s}^{-1}$ , what is the velocity of the $3.0\text{ kg}$ fragment?

10\text{ m s}^{-1}

due west

10\text{ m s}^{-1}

due east

15\text{ m s}^{-1}

due west

22.5\text{ m s}^{-1}

due west

Show answer & explanation

Answer: $10\text{ m s}^{-1}$ due west

Answer

10\text{ m s}^{-1}

due west

Before the explosion, the system is stationary, giving an initial momentum of

0\text{ kg m s}^{-1}

. By the law of conservation of linear momentum, the total momentum after the explosion must also equal zero. Taking the eastward direction as positive, the

2.0\text{ kg}

fragment has a momentum of

+30\text{ kg m s}^{-1}

. To balance this, the

3.0\text{ kg}

fragment must possess a momentum of

-30\text{ kg m s}^{-1}

, yielding

v = -10\text{ m s}^{-1}

, which means a speed of

10\text{ m s}^{-1}

directed due west.

Step-by-Step Solution

1

Determine the initial momentum of the system

p_i = 0\text{ kg m s}^{-1}

The object is initially at rest.

2

Express final total linear momentum using vector direction (let east be positive)

p_f = m_1 v_1 + m_2 v_2 = (2.0 \times 15) + (3.0 \times v_2) = 30 + 3 v_2

Linear momentum is conserved in an isolated system.

3

Equate initial momentum to final momentum and solve for

v_2

0 = 30 + 3 v_2 \implies v_2 = -10\text{ m s}^{-1}

The negative sign indicates the direction is opposite to east, which is due west.

Key Concept

Conservation of Linear Momentum in Explosions

Estimated Time:1m 30s

Question 13833Question →

Match each physical scenario or vector operation on the left with its corresponding physical property or resultant classification on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Particle in uniform circular motion pairs with a vector quantity of constant magnitude but changing direction; Dot product of force and displacement pairs with a scalar quantity representing work done; Two equal forces at 120 degrees pair with a resultant magnitude equal to P; Slope of displacement-time graph pairs with a vector quantity representing velocity.

Each physical scenario correctly corresponds to its fundamental vector/scalar classification or calculated resultant based on vector algebra.

Step-by-Step Solution

1

Analyze circular motion at constant speed

The velocity vector changes direction at every point, giving rise to centripetal acceleration directed toward the center.

Any physical quantity with direction is a vector quantity.

2

Evaluate the product of force and displacement vectors

W = \mathbf{F} \cdot \mathbf{d} = F d \cos\theta

, producing a scalar quantity (work done).

The dot product of two vectors yields a scalar.

3

Calculate the resultant of two equal vectors

P

at

120^\circ

R = \sqrt{P^2 + P^2 + 2P^2 \cos 120^\circ} = \sqrt{2P^2 - P^2} = P

.

Vector addition follows the law of cosines taking spatial angle into account.

4

Determine the physical quantity represented by the gradient of a displacement-time graph

\text{Slope} = \frac{\Delta s}{\Delta t} = v \text{ (velocity)}.

Displacement per unit time is velocity, a vector quantity.

Key Concept

Scalars, Vectors, and Vector Addition Laws

Question 13834Question →

Alhaji Sani purchased an industrial printing machine from a machinery merchant and paid in full, agreeing to collect the item the following morning. Before Alhaji Sani returned, the merchant sold and delivered the exact same printing machine to a second customer who bought it in good faith and without notice of the prior transaction. Under the Sale of Goods Act, what legal title does the second customer acquire to the machine?

A valid and complete title, because a seller who remains in possession of goods after sale can pass good title to a bona fide purchaser.

No title whatsoever, because property had already passed to Alhaji Sani under the general principle of nemo dat quod non habet.

A voidable title that terminates automatically once Alhaji Sani presents his original purchase receipt.

A temporary right of possession, which requires written ratification from Alhaji Sani to convert into full ownership.

Show answer & explanation

Answer: A valid and complete title, because a seller who remains in possession of goods after sale can pass good title to a bona fide purchaser.

Answer

The second customer acquires a valid title to the printing machine because under Section 25(1) of the Sale of Goods Act, a seller remaining in possession of goods after a sale can convey good title to a third party acting in good faith without notice of the previous sale.

Under Section 25(1) of the Sale of Goods Act, when a seller who has sold goods remains in possession of them or of the documents of title, the delivery or transfer of the goods under any sale by that seller to a person receiving them in good faith and without notice of the previous sale passes a valid title. The second purchaser is fully protected as a bona fide buyer for value without notice.

Step-by-Step Solution

1

Identify the primary legal rule governing transfer of title.

The general principle is 'nemo dat quod non habet' (no one can give what he does not have).

This rule protects true owners when non-owners attempt to sell their goods.

2

Examine the specific statutory exceptions to the nemo dat principle under the Sale of Goods Act.

Section 25(1) provides an exception for a 'Seller in Possession after Sale'.

Where a seller continues in possession of goods or documents of title after selling them, the delivery or transfer by that seller to any person receiving the same in good faith and without notice of the previous sale has the same effect as if authorized by the owner.

3

Apply the exception to the facts of the scenario.

The second customer paid for and took delivery in good faith without knowledge of Alhaji Sani's prior purchase.

Therefore, the second customer gets a valid legal title, and Alhaji Sani's remedy lies in damages against the merchant for breach of contract and conversion.

Key Concept

Exceptions to Nemo Dat Quod Non Habet: Disposition by Seller in Possession

Estimated Time:1m 15s

Question 13835Question →

In a limestone region characterized by well-jointed rock strata, rain water containing dissolved carbon dioxide percolates along vertical joints, expanding them into deep fissures separated by raised, flat-topped limestone blocks. Which landform corresponds to these remaining flat-topped blocks?

Clints

Grikkes

Stalagmites

Uvalas

Show answer & explanation

Answer: Clints

Answer

The correct answer is Clints, which are the flat-topped limestone blocks that remain standing between solutional fissures on a limestone pavement.

When rainwater containing dissolved carbon dioxide penetrates jointed limestone rocks, carbonation dissolves the calcium carbonate along vertical joints. The widened fissures are called grikkes, while the rectangular, flat-topped blocks left standing between them are known as clints.

Step-by-Step Solution

1

Identify the process and rock type described in the stem.

Chemical weathering via carbonation occurs on jointed limestone rock.

Carbonic acid in rainwater reacts with calcium carbonate along natural lines of weakness.

2

Distinguish between the positive (raised) and negative (depressed) landform components of a limestone pavement.

The vertical fissures widened by carbonation are grikkes, while the remaining exposed flat blocks are clints.

Solution selectively deepens joints, leaving the surrounding rock sections elevated relative to the grooves.

Key Concept

Limestone Pavement Features (Clints and Grikkes)

Estimated Time:1m 0s

Question 13836Question →

Match each discharge tube phenomenon or experimental setup in Column A with its correct physical description or property in Column B.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Faraday dark space matches the non-luminous region separating the negative glow from the positive column (

\approx 1\text{ mmHg}

); Crookes dark space matches the dark region around the cathode that expands at very low pressure (

\approx 0.01\text{ mmHg}

); Positive column matches the bright luminous stream extending toward the anode; Paddle wheel matches the demonstration of kinetic energy and mechanical momentum of cathode rays.

Each feature of discharge tubes corresponds to specific gas pressure stages and physical properties of cathode rays. Faraday dark space is the non-luminous region at moderate pressures; Crookes dark space expands near the cathode at very low pressure (

\approx 0.01\text{ mmHg}

); the positive column is the luminous glowing gas stream; and the paddle wheel experiment proves cathode rays possess mechanical momentum.

Step-by-Step Solution

1

Analyze discharge tube pressure stages.

At moderate pressures (

\approx 1\text{ mmHg}

), the Faraday dark space appears between the negative glow and the luminous positive column.

Ionization processes create distinct bright and dark regions based on electron acceleration distances between collisions.

2

Identify high-vacuum phenomena.

At very low pressures (

\approx 0.01\text{ mmHg}

), the Crookes dark space expands across almost the entire length of the discharge tube.

Fewer gas molecules allow electrons to travel longer distances without colliding, shifting ionization further down the tube.

3

Correlate mechanical experiments with cathode ray properties.

A paddle wheel mounted on glass rails rotates when hit by cathode rays, showing they possess momentum.

Electrons have mass

m

and velocity

v

, transferring kinetic energy and momentum (

p = mv

) upon impact.

Key Concept

Conduction of Electricity Through Gases and Cathode Rays

Question 13837Question →

Which of the following groups of African countries consists entirely of member states of the Economic Community of West African States (ECOWAS)?

Ghana, Senegal, and Côte d'Ivoire

Nigeria, Kenya, and Ghana

Senegal, Zambia, and Togo

Benin, Republic of the Congo, and Mali

Show answer & explanation

Answer: Ghana, Senegal, and Côte d'Ivoire

Answer

Ghana, Senegal, and Côte d'Ivoire consist entirely of member states of ECOWAS.

Ghana, Senegal, and Côte d'Ivoire are all located within West Africa and are member states of the Economic Community of West African States (ECOWAS).

Step-by-Step Solution

1

Define the regional mandate and geographic boundary of ECOWAS

ECOWAS is a regional trade bloc formed to promote economic integration exclusively among sovereign nations situated in West Africa.

Regional economic groupings are structured around distinct geographical zones across the African continent.

2

Examine the geographic regional affiliation of each nation listed in the options

Ghana, Senegal, and Côte d'Ivoire are all West African nations belonging to ECOWAS. In contrast, Kenya belongs to East Africa (EAC), Zambia to Southern Africa (SADC), and Republic of the Congo to Central Africa (ECCAS).

Identifying non-West African countries allows for the systematic elimination of incorrect option groupings.

Key Concept

Regional Economic Groupings and Trade Blocs in Africa

Question 13838Question →

Arrange the standard procedural steps involved in importing quota-restricted commercial goods through customs control into their correct sequential order from start to finish.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct chronological sequence begins with securing an import license or quota allocation, followed by submitting the Bill of Entry upon goods arrival, physical inspection and tariff duty assessment by customs, and concluding with duty payment and clearance release.

The process of clearing trade-restricted goods requires advance regulatory authorization (import license/quota allocation) before shipping. Upon arrival, the importer files a Bill of Entry with shipping documents. Customs authorities inspect the consignment to assess duties, and finally, duty payment allows the issuance of a release order.

Step-by-Step Solution

1

Identify the initial regulatory prerequisite

Securing an import license or quota allocation must take place before international trade transactions occur for restricted items.

Governments enforce trade quotas by requiring importers to obtain permission prior to shipping goods into the country.

2

Identify arrival declaration procedure

Submitting the Bill of Entry along with shipping documents follows shipment arrival at customs boundaries.

Formal customs processing cannot begin without the official declaration document detailing cargo value, origin, and description.

3

Determine customs evaluation step

Physical inspection and duty assessment take place after document submission.

Customs authorities must verify declared cargo against physical contents before computing the exact tariff liability.

4

Establish final release condition

Payment of assessed tariff duty and official cargo release form the final step.

Goods remain under customs custody until all statutory duties are settled and a release order is granted.

Key Concept

Customs clearance procedure and import quota enforcement

Question 13839Question →

Match each foreign trade commercial document listed on the left with its corresponding primary purpose or function on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Bill of Lading matches with serving as a document of title and shipping receipt; Certificate of Origin matches with declaring the manufacturing country for tariffs; Letter of Credit matches with providing a bank payment guarantee; Bill of Sight matches with allowing temporary customs clearance for inspection.

Each document is paired with its precise legal and operational definition in international commerce. Bill of Lading acts as a document of title and contract of carriage; Certificate of Origin states the manufacturing nation; Letter of Credit acts as a bank-backed payment security; and Bill of Sight is used for provisional customs inspection when complete shipping information is unavailable.

Step-by-Step Solution

1

Analyze the core legal and operational function of each commercial document in international trade.

Identified the primary role of each listed document in foreign trade operations.

Matching requires distinguishing shipping documents, customs forms, and financial guarantees.

2

Pair each document on the left with its corresponding functional definition on the right.

Paired Bill of Lading with document of title/receipt, Certificate of Origin with country declaration, Letter of Credit with bank payment guarantee, and Bill of Sight with missing details customs inspection.

Each definition is unique to its respective foreign trade document.

Key Concept

Functions of Commercial Documents in Foreign Trade

Question 13840Question →

A cell of electromotive force $E$ and internal resistance $r$ supplies a current of $1.2\text{ A}$ when connected across a $4.0\ \Omega$ resistor. When this resistor is replaced with a $10.0\ \Omega$ resistor, the current decreases to $0.6\text{ A}$ . Calculate the internal resistance $r$ of the cell in ohms ( $\Omega$ ).

Show answer & explanation

Answer: 2

Answer

The internal resistance of the cell is

2.0\ \Omega

.

For a complete circuit, the electromotive force

E

is related to load resistance

R

, internal resistance

r

, and current

I

by

E = I(R + r)

. Setting up equations for both load conditions gives

E = 1.2(4.0 + r)

and

E = 0.6(10.0 + r)

. Equating these expressions yields

4.8 + 1.2r = 6.0 + 0.6r

, which simplifies to

0.6r = 1.2

, giving an internal resistance of

r = 2.0\ \Omega

.

Step-by-Step Solution

1

Formulate the circuit equation for the first load resistance

E = 1.2 \times (4.0 + r) = 4.8 + 1.2r

Using Ohm's law for a complete circuit, the electromotive force equals current times total circuit resistance:

E = I(R_1 + r)

.

2

Formulate the circuit equation for the second load resistance

E = 0.6 \times (10.0 + r) = 6.0 + 0.6r

The cell maintains the same internal electromotive force

E

and internal resistance

r

with the new load resistor

R_2

.

3

Equate the expressions for

E

and solve for

r

4.8 + 1.2r = 6.0 + 0.6r \implies 0.6r = 1.2 \implies r = 2.0\ \Omega

Since

E

is constant for the cell, setting the two right-hand sides equal yields a single linear equation for the unknown internal resistance

r

.

Key Concept

Electromotive Force and Internal Resistance

Answer

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