Final answer:
The appropriate verb form to fill in the blank is 'duermen'.
Step-by-step explanation:
The appropriate verb form to fill in the blank is duermen. The subject of the dialogue is in the second person plural form 'Uds.', so the verb form should also be in the second person plural form. The correct conjugation for the verb 'dormir' (to sleep) in the second person plural is 'duermen'.
Learn more about Verb conjugation in Spanish