单项选择题

The tourist is prevented from entering a country if he does not have a (n) passport.

A．operative
B．effective
C．valid
D．efficient
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单项选择题
It ______ every day so far this month.
A．has rained
B．rains
C．rained
D．is raining
单项选择题
Scientists generally agree that the Earth's climate will warm up over the next 50 to 100 years ______ it has warmed in the 20000 years since the Ice Age.
A．as soon as
B．as long as
C．as much as
D．as well as
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