单项选择题

______ , he can quickly find out what's wrong with the machine.

A．Having been well trained
B．Having well trained
C．To be well trained
D．To have been well trained
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You'd better ______ the water until it has been boiled.
A．not to drink
B．not drink
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It's high time we ______ something to stop road accidents.
A．did
B．are doing
C．will do
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