单项选择题
What is a characteristic of all centrifugal cargo pumps? （）
A.They are self-priming B.Decreasing the speed of rotation will decrease the discharge pressure C.Opening the discharge valve wider will increase the discharge pressure D.All of the above
单项选择题 We’ve changed our（）not to start loading this evening．
单项选择题 We’ll put off（）until Friday．
单项选择题 We have finished（）and are ready for sailing．
