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Set 15: Form, Structure & Sense (Advanced)

Explanation

Answer: D

PASSAGE

The phenomenon of bioluminescence, though widely observed across marine _______ remains poorly understood in terms of its evolutionary origins and ecological functions.

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

A. species;
B. species:
C. species
D. species,✓ Correct

Detailed Answer Explanation

This question tests your understanding of sentence function and text organization. The phrase 'though widely observed across marine species' is a concessive clause that is parenthetical. A comma closes this clause before the main verb 'remains.' Each sentence in a well-constructed text serves a specific purpose. Consider what role this sentence plays in the argument: does it introduce, support, contrast, or conclude an idea? Understanding why an author includes specific sentences helps you grasp the overall argument. Each sentence should serve a clear purpose: introducing ideas, providing evidence, acknowledging counterarguments, or drawing conclusions. Identify the role to understand the structure.

Key Evidence:

• "The phenomenon of bioluminescence, though widely observed"

• "remains poorly understood"

Why others are wrong: A (A semicolon is too strong between a subordinate clause and main clause.), B (A colon doesn't fit between a subordinate clause and main clause.), C (Missing punctuation fails to properly transition from the subordinate to main clause.).

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