单项选择题

The millions of calculations involved, ______ by hand, would have lost all practical value by the time they were finished.

A．had they been done
B．they had been done
C．having been done
D．they were done
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单项选择题
No one can be ______ calm when facing with a great danger.
A．very
B．so
C．too
D．enough
单项选择题
You ______ him so severely; you should be tolerate to him.
A．shouldn't criticize
B．mustn't criticize
C．couldn't have been criticizing
D．shouldn't have been criticizing
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