Question

Perhaps the day will come ____ people will be able to breathe clean air in cities．

A．when

B．while

C．a(chǎn)s

D．since

Answer 1

A

這道題考查定語從句的用法：when引導(dǎo)定語從句修飾the day，因為在定語從句中缺少時間狀語，所以用when。句意是：可能人們在城市里能呼吸新鮮空氣的日子就到了。