The correct answer is C. Both...and
Step-by-step explanation:
In grammar, conjunction refers to a type of words that link different sections in a sentence or even sentences or clauses. In the case of correlating or correlative conjunctions these are conjunctions that are formed by two or more words that come pairs, which implies one pair cannot be used without the other and as in the case of any other conjunction they link different ideas, phrases or sentences this includes conjunctions such as either/or; neither/nor and both/and. Therefore in the sentence "Both Nalani and I are leaving so we can go to the movie" the correlating or correlative conjunction is "Both..and" and this are words that link two ideas in this case "Nalani" and "I" and also as a pair or unit.