单项选择题
Each crank is made up of two crank webs joined by a common（） to which the bottom endbearing is fitted.
A.throw B.crankshaft C.crankpin D.crosshead
单项选择题 During working, when the piston is near the （）, the air ignites the fine spray of fuel.
单项选择题 During the suction stroke, the piston is moving （）.
单项选择题 During the inspection, the starting air valves should be closed （） the engine from turning.
