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Difficulty: MediumCommas with Lists, Clauses, and Coordinate Adjectives

In the sentence below, a portion of the text is underlined.

"To determine the chemical composition of the ancient metal alloy, metallurgical technicians analyzed the structural properties of the sample, measured its thermal conductivity, recorded its magnetic susceptibility; and verified the presence of rare trace elements."

Which choice for the underlined portion best maintains parallel structure and correct list punctuation in standard written English?

  1. A
    NO CHANGE
  2. its magnetic susceptibility, and verifiedAnswer
  3. C
    its magnetic susceptibility and verifying
  4. D
    its magnetic susceptibility; verifying

Answer

The phrase 'its magnetic susceptibility, and verified' correctly uses a comma and coordinating conjunction to separate the final item in a series of parallel past-tense verbs.
The correct choice seamlessly maintains parallel structure by using the past-tense verb 'verified' to match 'analyzed', 'measured', and 'recorded'. It also correctly uses a comma before the coordinating conjunction 'and' to punctuate the series of four actions.

Step-by-Step Solution

1
Identify the sentence structure and list elements
The subject ('metallurgical technicians') performs a series of actions expressed as past-tense verb phrases: 'analyzed...', 'measured...', 'recorded...', and 'verified...'.
All items in a listed series must follow parallel grammatical construction.
2
Determine the correct punctuation rule for items in a series
Items in a list of three or more elements should be separated by commas, with a comma preceding the final coordinating conjunction ('and').
Semicolons are reserved for separating independent clauses or items in a complex list containing internal punctuation.
3
Evaluate the choices to select the grammatically correct option
The option offering 'its magnetic susceptibility, and verified' maintains both parallelism (past-tense verb) and correct serial comma placement.
It avoids inserting unnecessary semicolons or changing verb forms that disrupt parallel structure.

Key Concept

Commas with Lists and Parallel Structure
Estimated Time:1m 0s
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Topics

Commas with Lists, Clauses, and Coordinate Adjectives

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