问题
选择题
________ it comes to the increasing use of motor vehicles in the cities，some people think it should be limited．
A．Because
B．Once
C．When
D．While
答案
答案：C
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________ it comes to the increasing use of motor vehicles in the cities，some people think it should be limited．
A．Because
B．Once
C．When
D．While
答案：C
