Question

review: preterit tense -er & -ir verbs
-er/ir preterit
yo í nosotros/as imos
tú iste vosotros/as isteis
él/ella/usted ió ellos/ellas/ustedes ieran
¿qué ______ (comer) ayer tú?
comi
comiste
comieron

Explanation:

The question uses the subject tú (informal singular "you") and asks about a past action (marked by ayer = yesterday). For -ER verbs like comer, the preterite tense conjugation for tú uses the ending "-iste" as shown in the provided chart. Remove the "-er" ending from comer to get the stem com-, then add the ending.

Answer:

comiste