Final answer:
The appropriate form of the verb 'vestirse' in the given sentence is 'se visten'
Step-by-step explanation:
In this sentence, the appropriate form of the verb vestirse is se visten. The subject of the sentence is 'ellos', which means 'they' in English. The verb 'vestirse' means 'to dress oneself'. Therefore, the correct answer is option A - 'se visten'.
Learn more about Verb conjugation in Spanish