Answer:
Eli had walked the dog after he had finished his homework.
Step-by-step explanation:
Active voice is when the subject does the action (Eli had walked the dog instead of the dog had been walked by Eli) and perfect tense is when an action had happened and uses the verb to have. Parallel structure is when all of the verbs use the same tense. (Eli had walked the dog after he had finished his homework, not Eli is walking the dog after he had finished his homework. it does not make sense because it is using two verb tenses.)