Final answer:
The correct form of the verb vivir to complete the sentence "Él en San Juan" is vive.
Step-by-step explanation:
The correct form of the verb vivir to complete the sentence "Él en San Juan" is vive.
"Vive" is the third person singular form of the verb vivir (to live), which agrees with the subject "Él" (he).
For example: Él vive en San Juan. (He lives in San Juan.)
Learn more about Verb conjugation in Spanish