Shortly after publication, the book became ____ because of the writer’s repeated use of the negative word "nigger" to refer to the black Americans.

A．universal

B．conventional

C．controversial

D．skeptical

被最广泛接受的刷牙方法

A．水平颤动法

B．旋转刷牙法

C．Charter刷牙法

D．圆弧法

E．生理刷牙法