Correct answer:
anduvisteis
Anduvisteis is the conjugation of the verb andar that matches the second person plural (vosotros) in the preterite tense. The preterite tense is one of two simple past tenses. It is used to describe actions that took place or were completed at a certain point in the past. On the other hand, vosotros is an informal subject pronoun. It's more common for this pronoun to be used in Spain. Finally:
Vosotros anduvisteis al teatro.