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Difficulty: MediumClause Boundaries and Linking

During the Devonian period, the evolution of deep-rooting vascular plants fundamentally altered the planet's geochemical systems. By fracturing bedrock, these early plants accelerated the weathering of silicate rocks, which absorbed vast amounts of atmospheric carbon dioxide ______ this carbon draw-down contributed to a global cooling trend that eventually triggered a series of major glaciation events.

Which choice completes the text so that it conforms to the conventions of Standard English?

  1. A
    dioxide, but
  2. B
    dioxide,
  3. dioxide;Answer
  4. D
    dioxide

Answer

dioxide;
The sentence consists of two independent clauses: the first describing the absorption of atmospheric carbon dioxide, and the second explaining that this drawdown contributed to global cooling. Standard English conventions require two independent clauses to be joined by a semicolon, a period, or a comma with a coordinating conjunction. Using a semicolon correctly separates the clauses.

Step-by-Step Solution

1
Identify the boundary between the clauses and analyze their structure.
The text contains two distinct clauses: 'By fracturing bedrock, these early plants accelerated the weathering of silicate rocks, which absorbed vast amounts of atmospheric carbon dioxide' and 'this carbon draw-down contributed to a global cooling trend that eventually triggered a series of major glaciation events.'
Determining whether the clauses are independent or dependent dictates the required punctuation.
2
Determine if both clauses can stand independently.
Both clauses contain a subject and a verb and express a complete thought, making them independent clauses.
Independent clauses cannot be joined with just a comma or no punctuation; they require a semicolon, a period, or a comma and a coordinating conjunction.
3
Evaluate the choices based on standard punctuation rules and logical relationships.
The option containing a semicolon correctly links the two independent clauses. The option with a comma creates a comma splice, the option with no punctuation creates a run-on, and the option with 'but' introduces an illogical contrast.
A semicolon is the correct grammatical choice to connect closely related independent clauses without a conjunction.

Key Concept

Clause Boundaries and Linking
Estimated Time:1m 0s
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Topics

Clause Boundaries and Linking

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