Both ants and aphids benefit. Both ants and aphids are unaffected. The ants benefit and the aphids are harmed. The aphids benefit and the ants are unaffected.
I gave my students this multiple choice question: Aphids are small insects that sometimes live near ants. The ants protect the aphids from predators. The aphids produce a sweet substance that the ants eat. Which statement describes the relationship between ants and aphids?

Only one answer is correct among these 4 choices:
- Both ants and aphids benefit.
- Both ants and aphids are unaffected.
- The ants benefit and the aphids are harmed.
- The aphids benefit and the ants are unaffected.

Could you tell me which one is correct?

Both ants and aphids benefit.