How does King explore the word extremist to change its meaning in the letter?

A.) King argues that people trying to change the world for good, such as Jesus and Abraham Lincoln, could also be called extremists.

B.) King argues that other people, who only talk about racial issues, might be extremists, but he takes action, so he is not an extremist.

C.) King claims that he is proud to be considered an extremist by people who hold such racist views as those who criticized him.

D.) King insists that he is often frightened, not brave, so he cannot be an extremist.