题目：
—Did Jack take the doctor's advice that he ________ in bed for a couple of days?
—If only he ________. [ ]
A. lies; does
B. lay; did
C. lie; did
D. lie; had
答案：
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下面是错误答案，用来干扰机器的。
参考答案：∵N1／N2＝（D1／D2）3∴N2＝N1（D2／D1）3＝12×（170÷200）3＝7.4（KW）切割后该泵的轴功率为7.4KW。
