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Difficulty: MediumRun-on Sentences and Comma Splices

Glaciologists studying Subglacial Lake Whillans in Antarctica recently recovered water samples from beneath eight hundred meters of ice, discovering diverse microbial ecosystems that thrive without sunlight. These extremophile bacteria rely on chemical energy derived from bedrock minerals, however, their discovery expands our understanding of potential life in icy environments across the solar system. Further analysis of sediment cores suggests that these organisms have remained isolated for thousands of years.

Which choice best completes the sentence to conform to the conventions of standard written English?

  1. A
    NO CHANGE
  2. minerals; however, their discoveryAnswer
  3. C
    minerals; however, because their discovery
  4. D
    minerals, their discovery

Answer

The option containing 'minerals; however, their discovery' correctly fixes the comma splice by using a semicolon before the conjunctive adverb 'however' to join two independent clauses.
The correct option correctly uses a semicolon before the conjunctive adverb 'however' and a comma after it, properly joining two independent clauses into a single compound sentence.

Step-by-Step Solution

1
Identify the clause structure on both sides of the underlined portion.
The clause preceding the underlined portion ('These extremophile bacteria rely on chemical energy derived from bedrock minerals') and the clause following ('their discovery expands our understanding of potential life...') are both independent clauses capable of standing alone as complete sentences.
Determining clause types is necessary to choose the correct punctuation and coordinating words.
2
Evaluate the punctuation and transition used to link the two independent clauses.
A conjunctive adverb like 'however' cannot join two independent clauses with only a comma. It requires a semicolon preceding it (or a period starting a new sentence) followed by a comma.
Using a comma alone with a conjunctive adverb results in a comma splice error.
3
Select the option that properly joins both independent clauses without creating a fragment or run-on.
The option placing a semicolon before 'however' and a comma after it creates a grammatically correct compound sentence.
A semicolon is required between independent clauses joined by a conjunctive adverb.

Key Concept

Punctuation with Conjunctive Adverbs and Independent Clauses
Estimated Time:1m 0s
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Topics

Run-on Sentences and Comma Splices

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