20（）

单项选择题What s the meaning of the word defection (Last Line, Para. 6)（）

A．Customers" betrayal.
B．Service defects.
C．Customers" protection.
D．Service advertising.

单项选择题What does the author say about straight, horizontal bars painted across roads（）

A．They are suitable only on broad roads.
B．They are falling out of use in the United States.
C．They are ignored in a long period of time.
D．They cannot be used successfully to traffic circles.