单项选择题

The chemistry class ______ for five minutes when we hurried there.

A．had been on
B．was on
C．has been on
D．would be on
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单项选择题
The United States is composed of fifty states, two of ______ are separated from the others by land or water.
A．them
B．that
C．which
D．those
单项选择题
They discussed the problem three or four times, but could come to no
A．end
B．conclusion
C．result
D．judgment
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