Complete the sentence with the correct form of the verb in brackets: "The train has already ____ (leave) the station."

Explication

Has already builds a present perfect, which requires the past participle, and leave gives left. That one form fills both slots, so the train left at noon and the train has left carry the identical verb shape. The perfect meaning comes from the auxiliary, not from a separate participle, which is why nothing beyond the single past form is ever needed for this verb.