Answer:
I am positive the answer is C because I used to study the exact same lesson.
The number of oxygen atoms in a molecule
Well, put simply, biology is the study of life. Everything living is organic (everything living decomposes). Biologists study living things which have organic chemistry.
Well, depending on how long the migration is, many of the animals (mainly birds) could get sick and die, lowering the population. They could be shot by hunters, lowering the population. The children of the population could get left behind and lose their way, lowering the population. I'm not entirely sure how the population could grow other than them finding and staying with another group of their own kind. hope I was helpful! :)
I think the answer is Herbivores