I thought for sure that the correct answer is E man. Since life also started about 4 BYA (I think?), I thought it was just clarifying that time frame was likely when the event came and went. I guess I overthought it/brought too much outside knowledge into things.

Okay, it's confession time. I have to admit that I choose E, got frustrated that I missed it, used blind review to try again, and then just ended up choosing A anyway. However, this exercise still ended up being so meaningful to me because I think I did end up finding out something interesting about my psychology. In my mind, C was such a weak answer that captured so little that I thought there was no way it could be correct. I even caught the "actual trials" and "research intent" issues, but I was willing to overlook a flaw in order to get an answer I felt captured more of the situation. It feels kind of obvious while typing this now to say that its better to leave something out than to actively contradict something, but this has really changed what I think of now as an imperfect correct answer.

Nasty stuff man. All five of my answers were circled in BR, and I was convinced I completely bombed this. This was by far the best test of my confidence yet.