Final answer:
The appropriate form of the verb 'acostarse' to fill in the blank is 'te acuestas'.
Step-by-step explanation:
The subject of this question is Spanish.
The verb 'acostarse' means 'to go to bed' in Spanish. The appropriate form of the verb 'acostarse' to fill in the blank in the question is 'te acuestas', which is the second-person singular form.
Example: ¿A qué hora te acuestas tú? (What time do you go to bed?)
Learn more about Spanish verb conjugation