You observe two female fish of the same species breeding. one female lays 100 eggs and the other female lays 1000 eggs. which one of the following is least likely given the limits of fitness trade-offs?

Well, we know they're female fish of the same species. And know they were observed, so? Look, at the "keywords" "least likely given of fitness trade-offs" then you know the probability of which one is greater. if whoever you and anybody observed the two females you'll know key distinct qualities about both fish. So from what you learned what would be the most likely one would be and your answers below... 

the eggs from the female laying 1000 eggs have larger yolks than the yolks of the eggs from the female laying 100 eggs.

Ithink it true i might be wrong so don't take my word that its true.