Examkin

Identifying Underlying Assumptions

24 questions

All types24Multiple choice12Multiple select12
Question 21Question →

A metropolitan transit authority plans to replace its entire fleet of municipal diesel buses with electric buses powered by lithium-iron-phosphate batteries, claiming that this transition will significantly decrease the city's overall net greenhouse gas emissions over the next decade. The authority points to studies demonstrating that electric buses generate zero direct tailpipe emissions, whereas the current diesel fleet contributes twelve percent of the city's overall transportation-related carbon output.

Which of the following statements represent necessary assumptions upon which the transit authority's argument depends? Select all that apply.

Select all that apply

Show answer & explanation

Answer: The greenhouse gas emissions generated by the power plants supplying electricity to charge the new bus fleet will be lower than the tailpipe emissions eliminated by removing the diesel buses.; The total greenhouse gas emissions produced during the manufacturing and distribution of the electric buses will not exceed the operational emission reductions achieved over the ten-year period.

Answer

The argument relies on two necessary assumptions: that upstream electricity generation emissions will not exceed the tailpipe emissions eliminated, and that emissions from manufacturing the electric buses will not outweigh operational emissions savings over the ten-year timeframe.
The transit authority claims that replacing diesel buses with electric ones will achieve a net reduction in greenhouse gas emissions over ten years. This claim moves from a premise about operational tailpipe emissions to a conclusion about total net emissions. To bridge this gap, two unstated conditions must hold true: first, the indirect emissions created by power plants to charge the batteries must be lower than the tailpipe emissions eliminated; second, the embodied emissions created during battery and vehicle production must not exceed the operational savings accrued over the ten-year window. Applying the Negation Test confirms that if either condition fails, net emissions will not decrease.

Step-by-Step Solution

1
Deconstruct the argument into premises and conclusion.
Premise: Electric buses produce zero tailpipe emissions, replacing diesel buses that cause 12% of transit carbon output. Conclusion: Net greenhouse gas emissions will significantly decrease over the next decade.
Identifying the gap between operational tailpipe savings and total net emissions highlights unstated logical assumptions.
2
Apply the Negation Test to the statement regarding electricity generation sources.
Negation: Power plant emissions from charging the buses will equal or exceed eliminated tailpipe emissions. Under this negated condition, net emissions do not decrease, breaking the conclusion.
A statement is a necessary assumption if its negation invalidates the conclusion.
3
Apply the Negation Test to the statement regarding vehicle manufacturing emissions.
Negation: Upfront manufacturing emissions will exceed ten years of operational reductions. Under this negated condition, net emissions over the ten-year period will increase or remain neutral, invalidating the claim.
The conclusion specifies a net reduction within a ten-year timeframe, making lifecycle emissions within that window essential.

Key Concept

Identifying Unstated Necessary Assumptions using the Negation Test
Estimated Time:2m 0s
Question 22Question →

Forest ecologists observed that high-altitude pine trees infected with a native bark beetle species synthesize elevated levels of terpene resins, which effectively deter beetle oviposition. To protect commercial pine plantations at lower elevations from seasonal beetle outbreaks, the ecologists plan to treat young trees with a synthetic plant hormone that induces high terpene resin production prior to beetle emergence. They conclude that implementing this hormone treatment will significantly decrease beetle infestation rates in commercial plantations without relying on chemical insecticides. Which of the following is an assumption on which the forest ecologists' plan depends?

Show answer & explanation

Answer: The bark beetle populations in lower-elevation commercial plantations are not significantly more tolerant of terpene resins than the beetle populations in high-altitude forests.

Answer

The argument assumes that bark beetle populations in lower-elevation commercial plantations are not significantly more tolerant of terpene resins than high-altitude beetle populations.
The argument relies on the premise that stimulating terpene resin production in commercial pine trees will deter beetles from laying eggs. For this plan to succeed, the lower-elevation beetles targeted by the intervention must actually be susceptible to the deterrent effect of terpene resins. If lower-elevation beetles were highly tolerant of terpene resin, the hormone treatment would fail to prevent infestation, shattering the conclusion.

Step-by-Step Solution

1
Deconstruct the argument structure
Premise: High-altitude pine trees produce terpene resins that deter beetle oviposition. Plan: Apply a synthetic hormone to lower-elevation commercial trees to induce terpene resin production before beetle emergence. Conclusion: The treatment will significantly reduce beetle infestation rates in commercial plantations.
Identifying premises and the core conclusion establishes the logical gap that an underlying assumption must bridge.
2
Identify the unstated logical gap
The argument assumes that the deterrence observed in high-altitude forests will transfer effectively to low-elevation commercial plantations.
The plan relies on low-elevation beetles responding to terpene resins in the same deterrent manner as high-altitude beetles.
3
Apply the Negation Test to the candidate assumption
Negated statement: Lower-elevation beetles ARE significantly more tolerant of terpene resins than high-altitude beetles. If true, the elevated resin levels will fail to deter oviposition, completely undermining the conclusion.
A statement whose logical negation destroys the validity of the conclusion is a required unstated assumption.

Key Concept

Identifying Necessary Assumptions via the Negation Test
Question 23Question →

Paleoclimatologists analyzing sediment cores from an isolated subglacial lake in Antarctica discovered a sharp spike in micro-diamond concentrations in layers corresponding to 12,800 years ago. Because micro-diamonds typically form under the extreme temperatures and pressures generated by hypervelocity cosmic impacts, the researchers concluded that a comet impact caused the abrupt atmospheric cooling event recorded in the sediment layers from that era. Which of the following is an assumption upon which the researchers' argument depends?

Show answer & explanation

Answer: The micro-diamond spike in the sediment layers was not produced by terrestrial geological events, such as deep-mantle volcanic eruptions or tectonic shearing.

Answer

The argument assumes that the micro-diamond spike in the sediment layers was not produced by terrestrial geological events, such as deep-mantle volcanic eruptions or tectonic shearing.
The conclusion asserts that a comet impact caused the cooling event based solely on the presence of micro-diamonds. For this evidence to lead to that conclusion, the researchers must assume that no alternative, non-impact mechanisms (such as terrestrial volcanic or tectonic forces) produced the micro-diamonds. Negating this statement breaks the logical connection between micro-diamonds and the cometary impact hypothesis.

Step-by-Step Solution

1
Deconstruct the argument structure into premise and conclusion.
Premise: Micro-diamond concentrations spiked 12,800 years ago, and micro-diamonds typically form under extreme impact pressures. Conclusion: A comet impact caused the abrupt cooling event.
Identifying the link between the evidence (micro-diamonds) and the claim (comet impact) exposes missing logical bridges.
2
Apply the Negation Test to candidate assumptions.
Negating the statement regarding terrestrial sources yields: 'The micro-diamond spike WAS produced by terrestrial geological events (like volcanoes or tectonic shearing).'
If terrestrial processes created the micro-diamonds, then their presence no longer serves as evidence of a cosmic impact, completely invalidating the conclusion.

Key Concept

Identifying Necessary Assumptions via the Negation Test
Question 24Question →

Art conservators attempting to preserve a famous Renaissance oil painting observed severe micro-cracking caused by fluctuations in gallery humidity. To mitigate this without altering the gallery's environmental controls, conservators applied a newly synthesized nano-polymer sealant to test panels, where it successfully formed a moisture-impermeable barrier and prevented structural deformation under simulated humidity shifts. The conservators conclude that applying this sealant to the Renaissance painting will effectively protect it from further humidity-induced micro-cracking. Which of the following is an assumption on which the conservators' conclusion depends?

Show answer & explanation

Answer: The chemical interaction between the original paint layers of the Renaissance painting and the nano-polymer sealant will not degrade the sealant's moisture-impermeable barrier over time.

Answer

The argument depends on the assumption that chemical interactions between the Renaissance painting's paint layers and the nano-polymer sealant will not degrade the sealant's moisture barrier over time.
The conclusion asserts that applying the sealant to the painting will protect it based on success with test panels. For this transfer of results to hold, the painting's specific chemical composition must not degrade the sealant's core functional property (its moisture barrier). Negating this assumption breaks the logical bridge from test panel success to actual painting protection.

Step-by-Step Solution

1
Identify the argument structure (premises and conclusion)
Premise: Micro-cracking is caused by humidity shifts. Premise: Nano-polymer sealant formed an impermeable barrier on test panels and prevented damage during humidity shifts. Conclusion: Applying the sealant to the Renaissance painting will protect it from further humidity-induced micro-cracking.
Isolating the gap between test panel performance and actual application on the historical artwork reveals missing assumptions.
2
Apply the Negation Test to candidate assumptions
Negating the statement that chemical interactions will not degrade the sealant yields: 'Chemical interactions between the paint layers and sealant WILL degrade the sealant's barrier.'
If the barrier degrades upon contact with the painting's specific paint layers, the sealant cannot protect the painting, causing the conclusion to fall apart completely.

Key Concept

Identifying Necessary Assumptions using the Negation Test
PreviousPage 2 / 2
Identifying Underlying Assumptions Practice Questions — GRE General Test — Page 2 | Examkin