OG1 阅读 Q24

Choice D is the best answer. In (lines 12-14,"The...around") the authors state: "the first fea-ture of our structure which is of biological interest is that it consists not of one chain, but of two."
Choices A and B are incorrect because (lines 12-14,"The...around") explicitly state that it is the two chains of DNA that are of "biological interest," not the chemical formula of DNA, nor the common fiber axis those two chains are wrapped around. Choice C is incorrect because, while the X-ray evidence did help Watson and Crick to discover that DNA consists of two chains, it was not claimed to be the feature of biological interest.