单项选择题

The doctor will not perform the operation_________ it is absolutely necessary.

A．so
B．if
C．for
D．unless
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单项选择题
_________by the look on her face, she didn’’t catch what I meant.
A．Judging
B．Judged
C．Judge
D．To judge
单项选择题
The river here is very wide but_________, so you can walk across it.
A．narrow
B．arrow
C．shallow
D．hollow
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