单项选择题
A.head capacity to improve
B.discharge to be reversed
C.efficiency to decrease
D.slippage to decrease
单项选择题 Water allowed to accumulate in the hydraulic system oil will cause an oxidation process producing by- products which are normally （）.
单项选择题 If an anchor windlass has been idle for some time, you should （）.
单项选择题 The color of the flame on a halide torch without any refrigerant present is （）.