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Difficulty: MediumCommas with Nonessential and Parenthetical Elements

The single-celled slime mold *Physarum polycephalum* lacks a brain, yet it can solve complex mazes to find food. As it moves, the organism deposits a trail of translucent secretion behind it. This extracellular slime, which contains a chemical compound that is soluble, helps the mold navigate by signaling which paths it has already explored.

Which of the following choices best punctuates the underlined portion of the passage?

  1. NO CHANGEAnswer
  2. B
    compound, that is soluble, helps
  3. C
    compound that is soluble helps
  4. D
    compound that is soluble; helps

Answer

The correct choice is 'NO CHANGE' because it properly closes the nonessential clause with a comma while keeping the restrictive modifier free of punctuation.
The correct choice is the one that places a comma after 'soluble' to close the nonessential clause starting with 'which' without inserting commas around the restrictive modifier 'that is soluble.'

Step-by-Step Solution

1
Identify the main subject and verb, and locate any intervening clauses.
The main subject is 'This extracellular slime' and the main verb is 'helps.' The clause 'which contains a chemical compound that is soluble' is an intervening nonessential element.
Nonessential relative clauses must be enclosed by a pair of commas to separate them from the main sentence structure.
2
Analyze the sub-clause 'that is soluble' to determine if it is restrictive or nonrestrictive.
The clause 'that is soluble' is restrictive because it restricts the meaning of 'compound' to a specific type, so it must not have commas around it.
Restrictive clauses are essential to the meaning of a sentence and should not be set off by commas.
3
Combine these punctuation decisions to find the correct choice.
A comma is required after 'soluble' to close the nonessential clause, and no commas should surround 'that is soluble.' This corresponds to 'NO CHANGE.'
This choice correctly coordinates the punctuation of both the nonessential relative clause and the restrictive clause.

Key Concept

Commas with Nonessential and Parenthetical Elements
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Topics

Commas with Nonessential and Parenthetical Elements

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