Why Did Opera Singer Marian Anderson Perform an Open-Air Concert

Why did opera singer Marian Anderson perform an open-air concert on the steps of the Lincoln Memorial in 1939?

A) The event was a peace protest in the face of the coming war in Europe.
B) Performances at the Lincoln Memorial had been part of the African-American tradition in Washington DC since Reconstruction.
C) The Daughters of the American Revolution had refused to allow the black opera singer to perform at a concert hall.
D) A fire at the original venue - the Library of Congress - had forced Anderson and her audience to move outside.