Final answer:
The most appropriate form of the verb to complete the sentence is 'comió'.
Step-by-step explanation:
The most appropriate form of the verb to complete the sentence is A. comió. Mi hermano comió mucha comida ayer. In Spanish, the verb changes depending on the subject, and 'hermano' is singular, so 'comió' is the correct form for the third person singular (he/she) past tense of the verb 'comer' (to eat).
Learn more about verb forms in Spanish