The best answer for this question is:
C. You need to speak with Mr. McCarthy, Mrs. Sanchez, and Ms. Hoffman.
Always remember that the clause that precedes the colon mark should be an independent clause. It should contain both a subject and a predicate. In other words, you should not use a colon in situations like below:
a. The books you will need include: Treasure Island and The Swiss Family Robinson. (should have no colon after include)
The same thing with letters B and D.
