单项选择题

The ratio of the work done by the machine ______the work done on it is called the efficiency of the machine.

A．against
B．with
C．to
D．for
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单项选择题
A．the othersB．all othersC．theseD．those
A．the others
B．all others
C．these
D．those
单项选择题
A．HoweverB．MoreoverC．ThoughD．Therefore
A．However
B．Moreover
C．Though
D．Therefore
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