单项选择题

Much labor would have been saved if the electronic computers ______ before.

A．had invented
B．were invented
C．should have been invented
D．had been invented
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单项选择题
He must have had an accident, or he ______ here then.
A．would have been
B．had been
C．should be
D．could be
单项选择题
If only you ______ him what I said! Everything would have been all right.
A．didn"t told
B．hadn"t told
C．would not tell
D．would have not told
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