The answer was that the ratio of egg weight to bird size is higher for smaller birds than for larger birds.
Wait, why wasn't that one A? I thought it was that some different species have different egg sizes (A) (paraphrased greatly - my memory is quite hazy at this point). How can you infer that the ratio is higher for small birds when you were only given 3 birds as evidence? Why do those birds have to be indicative of all birds? Couldn't they be exceptions to the general rule? Of course, I feel like crap after taking this test so chances are I am wrong.
I'm pretty sure I chose the ratio of egg weight to bird size is higher for smaller etc. answer. Some of the others looked good, but they talked about egg size. The passage didn't talk about egg size, only weight.