There's a subtle disconnect here - just because something is a product of chance, does it mean it will not bear on the investigator's goal? Let's say there is a freak accident in the lab. If the results of that have nothing to do with the stated goal of the research, then according to the rules of modern, funding-centric science, they'll be ignored. But what if EUREKA something relevant appears. Would the researchers ignore it because it was because of chance? No, they'd only ignore it if it did not bear on the research.
(A) states the assumption, and, in short, tells us that if something is a chance discovery, it's irrelevant (this is the contrapositive of what's given, relevant --> purposefully seeks). This completes the argument: Not on purpose --> irrelevant --> not focus on it (and thus not learn from it).
(B) is incorrect because it is irrelevant whether past investigators made predictions. Even if they had, they were not bound to only focus on their goals, which is the core of the argument.
(C) is out of scope -- preferences?
(D) focuses on who receives grants, which is off topic
(E) is out of scope -- most valuable? The argument states "many", not "most valuable."
, I didn't. I ended up getting a basic sense of core:
