Why Was There Debate by Civil Rights Supporters Over Whether

Why was there debate by civil rights supporters over whether to directly challenge the "separate but equal" standard?

A) It was unclear whether the Supreme Court was ready to take that step.
B) They were having a lot of success with the more piecemeal approach.
C) There were few cases that made the legal principle clear.
D) Some of them believed more strongly in black separatism.
E) They believed they could have more success at the state level.