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Set 15: Form, Structure & Sense (Intermediate)

Explanation

Answer: C

PASSAGE

The ecosystem's resilience depends not only on species diversity but also on the complex interactions among species, each of which _______ a unique ecological role.

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

A. have played
B. playing
C. plays✓ Correct
D. play

Detailed Answer Explanation

This question tests your understanding of sentence function and text organization. 'Each of which' is singular (each species plays a role). The relative pronoun 'which' refers to 'species,' but 'each' makes it singular. 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:

• "species...each of which"

• "a unique ecological role"

Why others are wrong: B ('Playing' is a participle; the relative clause needs a finite verb.), A ('Have played' is plural; 'each' is singular.), D ('Play' is plural; 'each' is singular.).

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