Explanation
Correct answer: A.
Choice A is the best answer because it most accurately describes the function of the underlined sentence. The sentence indicates that scientists used time-lapse photography during both day and night to detect pollinators visiting red clover. Therefore, the underlined sentence has the function of describing an approach scientists used in the pollinator study discussed in the text.
Why the other choices are wrong
Choice B
Choice B is incorrect because the underlined sentence discusses equipment the scientists used to conduct their study, and the text provides nothing to suggest these elements of their experimental design could, by themselves, question claims resulting from the study.
Choice C
Choice C is incorrect because nothing in either the underlined sentence or the rest of the text addresses whether moths have a preference for red clover or any other flowers.
Choice D
Choice D is incorrect. Although the sentences that follow the underlined sentence discuss research findings, nothing in the text suggests that these findings were unexpected. Moreover, the underlined sentence describes part of the scientists’ experimental design (day and night time-lapse photography), not a finding of the scientists’ study.