Final answer:
The correct form of the verb 'comer' to fill in the blank in the question is 'come'.
Step-by-step explanation:
The correct form of the verb comer to fill in the blank in the question is come. The question is asking 'What do you eat, Professor?'. The verb 'comer' is conjugated in the third-person singular form 'come' to match the pronoun 'Ud.' which stands for 'usted' meaning 'you' (formal) in Spanish.
Learn more about conjugation of the verb 'comer' in Spanish