Here's a problem to solve: Which statement describes how muscles work to allow a person to extend an arm from a curled position by straightening the elbow?

Among the 4 following options, which is the correct answer?

- A: Both the biceps and triceps contract.
 
- B: Both the biceps and the triceps relax.
 
- C: The triceps contract and the biceps relax.
 
- D: The biceps contract and the triceps relax.
 