Question

ar preterit
yo é nosotros/as amos
tú aste vosotros/as asteis
él/ella/usted ó ellos/ellas/ustedes aron
¿qué ______ (jugar) ustedes ayer?
jugó
jugaron
jugamos

Explanation:

The question uses the subject "ustedes" (plural formal "you") and asks about a past action ("ayer" = yesterday). For -AR verbs in the preterite, the ending for "ustedes/ellos/ellas" is -aron. The verb "jugar" is an -AR verb, so we remove the -ar and add -aron, resulting in "jugaron".

Answer:

jugaron