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Lina is preparing for her first international flight. ✈️ Select ALL the options that could correctly complete the sentence below.
"Passengers ___ show a valid passport at the check-in counter."
The correct answers are must, have to, and need to.
Showing a passport at check-in is an obligation, so we need a modal that expresses necessity. Must, have to, and need to can all express that something is required. "Don't have to" means it is not necessary (the opposite meaning), and "mustn't" means it is prohibited — neither fits the context of a requirement.