The correct answer is C. Will wear all black
Step-by-step explanation:
A sentence with a parallel structure is one in which the grammatical forms or patterns are consistent. In the case of the sentence, "He was tall, quiet, and" the adjectives "tall" and "quiet" create a parallel structure that would be completed if another adjective is added. This implies the ending that will not create a parallel structure is "will wear all black" because this does not contain an adjective but contains a verb. On the other hand, other options such as "very mysterious", "somewhat handsome" and "well dressed" are all adjectives and would create a parallel structure.