to control population size to pollinate their flowers to remove dead wood to aid in seed distribution
I gave my students this multiple choice question: Why do trees like oaks and walnuts depend upon squirrels?

Only one answer is correct among these 4 choices:
- to control population size
- to pollinate their flowers
- to remove dead wood
- to aid in seed distribution

Could you tell me which one is correct?

to aid in seed distribution