Fill in the blank with an appropriate modal:
He is ill. He ___ see a doctor.

Correct option is D

The appropriate modal is "must" because it conveys a strong obligation or necessity. When someone is ill, seeing a doctor is a crucial action, and "must" emphasizes the importance of this necessity.
Information Booster:
1. Can: Expresses ability or possibility.
2. Would: Indicates hypothetical or polite intentions.
3. Could: Suggests possibility or past ability.
4. Must: Denotes strong obligation or necessity.