The relationship is competitive. The relationship is cooperative. The relationship is parasitic. The relationship is predatory.
I gave my students this multiple choice question: Sofia put a bat house in a tree in her yard. The bats ate mosquitos in Sofia's yard at night and roosted in the house during the day. Droppings from the bat house nourished the tree. What kind of relationship exists between Sofia, the bats, and the tree?

Only one answer is correct among these 4 choices:
- The relationship is competitive.
- The relationship is cooperative.
- The relationship is parasitic.
- The relationship is predatory.

Could you tell me which one is correct?

The relationship is cooperative.