单项选择题

The machine ______, the next step was how to operate it.

A．having been installed
B．had been installed
C．having being installed
D．has been installed
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单项选择题
Foolish ______ she is, she will not make the same mistakes twice.
A．if
B．with
C．of
D．as
单项选择题
The French singer who had been praised very highly ______ to be a great disappointment at the evening show.
A．turned up
B．turned out
C．turned off
D．turned down
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