Final answer:
The appropriate preterite form of the verb dormirse is 'se durmieron'.
Step-by-step explanation:
The preterite form of the verb dormirse is se durmieron. In the sentence, Ana y Teresa se durmieron en el autobús, the reflexive pronoun 'se' is used to indicate that Ana and Teresa fell asleep. The preterite form 'se durmieron' is used to show that this action happened in the past.
Learn more about Verbs in Spanish