用磨床磨削平面时应（）。
A、检查磁盘吸力是否正常
B、接触面较小的工件，前后要放挡块、加档板
C、站立在砂轮正面
参考答案：A, B
— Do you know if it ______ tomorrow?
— Sorry, I don't know. If it ______, we will go fishing. [ ]
A.Will rain, won't rain
B.Will rain, doesn't rain
C.rains, won't rain
D.rains, doesn't rain
企业的最终目的是追求（）。
A、效率
B、效益
C、利益
D、利润
