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

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单项选择题

We’ve changed our（）not to start loading this evening．

A.heart
B.hearts
C.mind
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单项选择题

We’ll put off（）until Friday．

A.to discharge
B.discharge
C.discharging
D.to be discharging