Ornithologists have discovered why Arctic Terns fly such long distances to the Antarctic during migration ______ the polar summer at the destination provides 24 hours of daylight, allowing for constant feeding.
Which choice completes the text so that it conforms to the conventions of Standard English?
incentives:
incentives,
incentives while
incentives
Correct Answer: A
Choice A is the best answer. It uses a colon to introduce an explanation. The second clause ("the polar summer...feeding") explains the specific "incentives" mentioned in the first clause.
Choice B is incorrect because it creates a comma splice by joining two independent clauses with only a comma. Choice C is incorrect because "while" suggests simultaneous action rather than an explanation, and the punctuation logic is less precise than the colon for this structure. Choice D is incorrect because it creates a fused sentence with no punctuation between independent clauses.