Why Did the Women's Suffrage Movement Aim at a Constitutional

Why did the women's suffrage movement aim at a constitutional amendment?

A) State legislatures consistently opposed efforts to grant the right to vote to women.
B) The Supreme Court ruled against efforts to apply the Fourteenth Amendment to women.
C) Ordinary legislation that Congress had passed had proved ineffective.
D) The experience of African Americans showed that only a constitutional amendment could quickly and effectively guarantee the right to vote.
E) An amendment was perceived as the easiest path to equal rights.