How did the Democratic Party's support of the Civil Rights Act of 1964 lead to a change in its membership?

A- It led to the withdrawal of many rural farmers
B- It led to the withdrawal of many urban workers
C- It led to the withdrawal of many members of the North
D- It led to the withdrawal of many members in the South
My answer is D (Can someone please tell me if Im right or wrong?) If im wrong is there any website to help me out?