[单项选择]There was on shop in the town of Mufulira, which was notorious for its color bar. It was a drugstore. While Europeans were served at the counter, a long line of Africans queued at the window and often not only were kept waiting but, when their turn came to be served, were rudely treated by the shop assistants. One day I was determined to make a public protest against this kind of thing, and many of the schoolboys in my class followed me to the store and waited outside to see what would happen when I went in.
I simply went into the shop and asked the manager politely for some medicine. As soon as he saw me standing in the place where only European customers were allowed to stand he shouted at me in a bastard language that is only used by an employed when speaking to his servants. I stood at the counter and politely requested in English that I should be served. The manager became exasperated and said to me in English, "lf you stand there till Christmas I will never serve you."

A. a bar which is painted in different colors
B. the fact that white and black customers are served separately
C. a bar of chocolate having different colors
D. a counter where people of different colors are served with beer