Let's first look at why (D) is correct. The sentence in question is "muscle memory is a puzzling phenomenon." If we look at the first sentence of passage B, we see that the author brings up the idea of "muscle memory" in weightlifters and then goes on to say that "scientists think they know why" it occurs. In the second paragraph of passage B, the author cites a study that helps potentially explain this process. As a result, it is fair to say that passage B thinks that new research has shed light on the issue, which is what (D) states.
As for (B), there is simply no textual evidence for it. Passage B doesn't even talk about what athletes experience, much less compare their experiences to their cellular processes. If you have a part of the passage that you think supports (B), would be glad to take a look at it with you. Hope this helps!