单项选择题

The Egyptians ______ copper as early as 5,000 years before Christ.

A．they were using
B．having used
C．may have used
D．using
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单项选择题
My petrol tank was empty so I pulled into a garage to ______.
A．fill up
B．speed up
C．blow up
D．wind up
单项选择题
Just then we had an important piece of work in hand, the generator that supplies the power to the whole works broke ______.
A．out
B．up
C．off
D．down
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