Thanks Charles for sharing your thoughts as well!

I agree with the answer of D, although I want to highlight the key phrase of "biotic factor" that I also think is important and can make things a little easier.

Factors that may limit a population are often split into "biotic" or "abiotic" factors. Biotic ones are the ones that actually depend on living things, such as food supplies, other predators, etc. Abiotic factors are other non-living factors or chemical factors. Thus, while you could make an argument that any of the factors could have an effect on the growth rate, A, B, and C would probably be considered abiotic factors.

Iris, hope this helps. If needed I can try to expand some more or find some other explanations as well!