Final answer:
The correct way to express 'They fell asleep' in Spanish is 'se domieron'
Step-by-step explanation:
The correct way to express 'They fell asleep' in Spanish is se domieron. The verb 'dormir' means 'to sleep' and the reflexive pronoun 'se' is used to indicate that the action happened to themselves. So, 'se domieron' translates to 'they fell asleep'.
Learn more about Spanish verbs