Why Did Congress Pass the Voting Rights Act of 1965

Why did Congress pass the Voting Rights Act of 1965?

A) the Supreme Court had determined that only the national government could regulate elections -Consider This: Despite the Voting Rights Act,each state is still largely in control of the voting rules within that state.
B) because it was clear that many areas in the South had no intention of living up to the spirit of the Fifteenth Amendment
C) because Congress was afraid the Reverend Martin Luther King Jr.would lead a boycott of white businesses if the legislation was not passed
D) to prevent the race riots from spreading from African American neighborhoods into traditionally white neighborhoods