Answer choice C says that birds eating at feeders are more vulnerable to predators THAN are birds foraging naturally.

IF--as the stimulus suggests--the mild winter led more birds to forage naturally instead of relying on feeders, THEN fewer birds were exposed to the higher risk of predation associated with feeders. That means fewer birds would have been killed by predators this year compared to a typical winter (AKA, there is a larger-than-usual bird population this year).

I like to use hypothetical numbers sometimes to help me understand things more clearly. So, imagine that in a normal year, 1,000 birds feed at feeders, and 50% fall prey to predators—so 500 die. But this year, with the mild winter, maybe only 100 birds use feeders, resulting in just 50 deaths. That’s 450 fewer deaths due to predation, which naturally leads to a higher surviving bird population.

So, the mild winter indirectly caused a larger-than-usual bird population by reducing predation through decreased feeder usage.

Hope that helps clarify things—this one’s a bit tricky!

It seems like you're confusing the relationship between years of training (YT) and being extraordinarily disciplined (D).

Since YT requires D, it can be diagrammed in Lawgic as: YT → D

Your statement (Tom does not have years of training and therefore is not extraordinarily disciplined) can be diagrammed as: /YT → /D

This is a mistaken negation. The contrapositive of the premise should be: /D → /YT

Therefore, if Tom does not have YT (aka /YT), then, him not being extraordinarily disciplined (aka /D) is an invalid conclusion.