Colon only introduces a list.
B. A colon points to an idea in an earlier sentence.
C. A colon can't be used in a question.
D. The words coming before the colon must form a complete sentence.
I would say that the correct answer about the use of a colon is the first one - colon only introduces a list. I know for sure that B and C aren't correct, but I am not completely sure about D.
