Final answer:
The verb that completes the sentence is 'saliste'.
Step-by-step explanation:
The verb that correctly completes the sentence is saliste.
The sentence is asking 'At what time did you (singular) _____?'. Since the subject of the sentence is 'tú' (you singular) we need to use the corresponding verb form. In this case, the correct verb form is 'saliste', which is the second person singular preterite form of the verb 'salir' (to leave/go out).
For example, 'A qué hora tú saliste?' translates to 'What time did you leave?'
Learn more about Verb conjugation in Spanish