Both the biceps and triceps contract. Both the biceps and the triceps relax. The triceps contract and the biceps relax. The biceps contract and the triceps relax.
I gave my students this multiple choice question: Which statement describes how muscles work to allow a person to extend an arm from a curled position by straightening the elbow?

Only one answer is correct among these 4 choices:
- Both the biceps and triceps contract.
- Both the biceps and the triceps relax.
- The triceps contract and the biceps relax.
- The biceps contract and the triceps relax.

Could you tell me which one is correct?

The triceps contract and the biceps relax.