单项选择题

A new technique ______ , the gross output increased by 20 percent.

A．working out
B．having worked out
C．having been worked out
D．to have been worked out
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单项选择题
Please take what you like, you ______ eat too much.
A．may not
B．would not
C．must not
D．can not
单项选择题
On the beach she could hardly ______ him from the other swimmers.
A．figure
B．tell
C．recognize
D．know
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