Answer: The correct answer is b) both verbs to the present tense or change both verbs to the past tense.
Step-by-step explanation:
A parallel structure, also known as parallelism, is the repetition of a chosen gramatical structure in a sentence. It means that the two verbs (in this case) must follow the same pattern, so if the first one is in present the second one should be in the same tense; if past is chosen, it means that both verbs must be in past, so B is correct.