单项选择题

They ______ us since five o'clock this morning until now.

A．are helping
B．help
C．have helped
D．have been helping
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单项选择题
We think it possible ______ the local government will be able to solve the housing problem.
A．for
B．that
C．when
D．how
单项选择题
By next week the new regulations ______.
A．will introduce
B．are to introduce
C．are to be introduced
D．will have introduced
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