Answer:
Usually either B or C. Can be A if it's used during quotes. [see explanation - question contains nuance]
Step-by-step explanation:
Honestly, it depends. Usually, an ellipsis is used in speech to show that the character is thinking and drifting off. If it's in a non-fiction formal piece of persuasive writing, then it would be B. Otherwise, if it's an essay and it's used in a quote, it's A. Usually though, it would be C.
Depends on context.