Question

ar preterit
yo é nosotros/as amos
tú aste vosotros/as asteis
él/ella/usted ó ellos/ellas/ustedes aron
¿quién ______ (invitar) a la fiesta tú?
invitaste
invitó
invitè

Explanation:

The question targets the subject "tú" (you informal singular) and uses the preterite tense for the -ar verb invitar. The preterite ending for "tú" -ar verbs is "-aste", so we remove the "-ar" from invitar and add "-aste".

Answer:

invitaste