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Difficulty: HardCommas with Lists, Clauses, and Coordinate Adjectives

Choose the option that best maintains the sentence's standard written English grammar and punctuation.

To improve the shelf life of the organic packaging, the food chemist synthesized a flexible, transparent, starch film, but the material degraded too quickly under humid conditions.

Which of the following is the best choice for the underlined portion of the sentence?

  1. A
    NO CHANGE
  2. flexible, transparent starch film, but the materialAnswer
  3. C
    flexible, transparent starch film; but the material
  4. D
    flexible, transparent starch film, the material

Answer

The correct answer is the option that correctly separates the coordinate adjectives with a comma, leaves the cumulative adjective unpunctuated, and uses a comma before the coordinating conjunction to join the two independent clauses.
The correct option correctly handles both adjective punctuation and clause separation. First, 'flexible' and 'transparent' are coordinate adjectives because they can be reversed ('transparent, flexible') and can be joined by 'and' ('flexible and transparent'), so they must be separated by a comma. Conversely, 'starch' is a cumulative adjective because it directly modifies the noun 'film' and cannot be naturally reordered (we would not say 'starch, transparent film' or 'transparent and starch film'), so no comma should separate 'transparent' and 'starch'. Second, the sentence contains two independent clauses joined by the coordinating conjunction 'but', which requires a preceding comma to prevent a run-on sentence.

Step-by-Step Solution

1
Analyze the relationship between the adjectives modifying 'film'.
The adjectives are 'flexible', 'transparent', and 'starch'. 'Flexible' and 'transparent' are coordinate adjectives (they can be reversed or joined by 'and'), so they require a comma between them. 'Starch' is a cumulative adjective because it cannot be reversed with the other adjectives (e.g., 'starch, transparent film' is incorrect), so no comma should precede or follow it.
Correctly identifying coordinate versus cumulative adjectives determines where commas are needed within the noun phrase.
2
Identify the clause structure of the sentence.
The sentence consists of an introductory dependent clause followed by two independent clauses: 'the food chemist synthesized...' and 'the material degraded...'.
Determining clause boundaries is essential for choosing the correct punctuation to join them.
3
Select the punctuation that correctly connects the two independent clauses.
Two independent clauses must be joined either by a semicolon alone, or by a comma followed by a coordinating conjunction (such as 'but'). The option with a comma and 'but' correctly connects the clauses without creating a comma splice or using an incorrect semicolon-conjunction combination.
Applying standard punctuation rules for independent clauses ensures grammatical correctness.

Key Concept

Commas with Lists, Clauses, and Coordinate Adjectives
Estimated Time:1m 0s
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Topics

Commas with Lists, Clauses, and Coordinate Adjectives

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