Answer:
C.) will pick up
Explanation:
Adverb clauses are groups of words with at least a subject and a verb and whose function is to modify or describe adjectives, verbs or other adverbs. They, therefore, provide information about time, place, reason, manner, condition, frequency or degree and are usually introduced by subordinate conjunctions such as when, where, since, because, while, although, after, as, as if, before, so that, unless, even, and until.
In the sentence, the adverb clause, which it's “when school is out,” modifies the verb phrase “will pick up” by providing information about time (It answers the question: When will the bus pick up the children?)
