Martin Luther King, Jr., is well known for his work in civil rights and for his many famous speeches, among them his moving "I Have A Dream" speech. But fewer people know much about King's childhood. M. L., as he was called, was born in 1929 in Atlanta, Georgia, at the home of his maternal grandfather. M.L.'s grandfather, the Reverend A. D. Williams, purchased their home on Auburn Avenue in 1909, 20 years before M. L. was born. The Reverend Williams, an eloquent speaker, played an important role in the community since so many people's lives centered around the church. He allowed his church and his home to be used as a meeting place for a number of organizations dedicated to the education and social advancement of blacks. M.L. grew up in this atmosphere, with his home being used as a community gathering place, and was no doubt influenced by it.

M. L.'s childhood was not especially eventful. His father was a minister and his mother was a musician. He was the second of three children, and he attended all-black schools in a black neighborhood. The neighborhood was not poor, however. Auburn Avenue was the main artery through a prosperous neighborhood that had come to symbolize achievement for Atlanta's black people. It was an area of banks, insurance companies, builders, jewelers, tailors, doctors, lawyers and other black-owned or black-operated businesses and services. Even in the face of Atlanta's segregation, the district thrived. Dr. King never forgot the community spirit he had known as a child, nor did he forget the racial prejudice that was a seemingly insurmountable barrier that kept black Atlantans from mingling with whites.

What is this passage mainly about？

A．The prejudice that existed in Atlanta.

B．Martin Luther King's childhood.

C．M. L.'s grandfather.

D．The neighborhood King grew up in.