Why D?

Hello @samlhoover, I found support for answer choice D in the last paragraph, but I understand your confusion. The passage states, "As they have expanded their targets to 20 more semiconductor materials, their cache of crystal-manipulating peptides has ballooned into the hundreds" (line 52.) It doesn't explicitly state that they succeeded in reaching their targets. However, this sentence seems to imply that testing a wider variety of semi-conducting materials has allowed them to discover more peptides. For this to be true, binding would have to occur. The last paragraph does strongly suggest that their project has been successful. This is enough for me to choose answer choice D, especially considering that the other answer choices have much bigger problems.

Can you elaborate on those problems?

Given that this is a must be true passage, wrong answer choices will be ones that simply are not stated in the passage. We do not have any proof for A, B, C, or E.