Use had better (negative: had better not) and the verb in brackets to complete the urgent warning: The last cable car departs in four minutes. We ___ now, or we will be stranded overnight. (leave)

Բացատրություն

The instruction requires had better, and had better leave uses its required bare infinitive while warning of an immediate bad consequence. Must leave can also express urgency, but it does not satisfy the construction prescribed in the prompt.