Choose the sentence that correctly uses a modal of necessity.

Tom just started a new job at a restaurant. The manager told him about the dress code.

The correct answer is "You have to wear the uniform — it's required every day."

"Have to" expresses an external obligation or rule. Since the uniform is required, "have to" fits perfectly. The other options contradict the second part of the sentence: "don't have to" and "don't need to" mean it's optional, and "must not" means it is forbidden — the opposite of what's intended!