Final answer:
The correct form of the verb in the imperfect tense in this sentence is 'llegaba', which means 'he was arriving'.
Step-by-step explanation:
The correct form of the verb in the imperfect tense in this sentence is llegaba. The imperfect tense is used to describe ongoing or repeated actions in the past. Since the sentence is talking about the past actions of the waiter, the correct form is 'llegaba', which means 'he was arriving'.
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