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
【正确答案】：C
【题目解析】：【答案】C 【译文】机器所做的工作与在机器上所用的功之比，就称为机器的效率。 【考点】固定搭配 【解析】题中ratio与介词to是固定搭配，the ratio of A to B的意思为“A与B之比(率)”，故选C
