Answer:
The correct pronoun to complete the sentence is "he".
Step-by-step explanation:
The correct sentence goes " After Jim, Stacey, and he finished lunch, they relaxed in the sun. The options given are a subject pronoun and an object pronoun, then it depends of where is the pronoun located to determine the use of the correct one, if it is before the verb it would be a subject one, but if it is after the verb it would be an object one, here it is located before the verb, therefore, the correct option is "he"