单项选择题
A.counterbalance the crank throws on the crankshaft
B.keep the engine running smoothly between power stroke
C.provide a belt-driving surface for the operation of auxiliary machinery
D.prevent the engine from overspeeding
单项选择题 The pumps press oil into the cross-head bearing gap when the load on the shell is at its lowest What is the meaning of “its” in the sentence above?（）
单项选择题 The pumps employed on board ship can be divided into two main categories ie（） pumps and centrifugal pumps.
单项选择题 The pump has a constant stroke and the amount of fuel delivered is regulated by rotating （） which has a specially arranged helical groove cut into it.