The diagram below shows groups that were involved in the planning of the March on Washington:

A list diagram titled Organizers of the March on Washington. The following groups are listed: Student Nonviolent Coordinating Committee, National Urban League, Congress on Racial Equality, and National Association for the Advancement of Colored People. Below the list is a question mark.

Which organization also belongs on this diagram?

Black Panther Party
American Civil Liberties Union
National Organization of Women
Southern Christian Leadership Conference