Question

Tropical forests play a key role as the world's carbon and wildlife reservoirs.

• A. Play a key role as the world's
• B. Had played a key role in the world's
• C. Have been played a key role at the world's
• D. Has played a key role for the world's

Hint:

Decide if the tense fits a general, permanent fact, and whether 'as' is the right preposition for the meaning intended.

Answer 1

The Correct Option is A

The sentence states a general, timeless fact about tropical forests, so the simple present tense is correct here. "Play" agrees with the plural subject "forests", and "as" correctly means "in the capacity of", matching the sense of forests acting as reservoirs.

1. Option A: "play a key role as the world's" uses the right tense, the right subject-verb agreement, and the right preposition "as" to mean "in the role of". Nothing needs to change.
2. Option B: "had played" is past perfect, wrongly suggesting the role ended before some other past event, which contradicts the ongoing, general truth of the sentence.
3. Option C: "have been played" is a passive construction that does not fit here, because forests are the ones performing the role, not receiving an action.
4. Option D: "has played" wrongly treats "forests" as singular, and "for the world's" changes the meaning from "acting as" to "on behalf of".

Since the underlined part has no error, option A, "no error", is correct.