The right answer to this question is option B. number of predators present.
What you need to pay attention in this question is the word "biotic".
Explanation:
With that said, we need to understand this term in order to answer the question properly, so, what is a biotic factor? By your own knowledge you can say that the word "bio" means life right? If so, we already know more than half of the answer because, if it means life, all the alternatives that don't have anything to do with living beings we can say they aren't correct. Let's see, the first one tells us about the local geography, of course it can affect the size of a population, due to air pressure for example, but is it a biotic factor? No, life doesn't have any influence here. The yearly temperature and precipitation are the same, they don't talk about living beings, so the only right alternative is the one that talks about predators, that are actual living beings influencing in an ecosystem.
