单项选择题
In each cylinder cover there are two or three holes for （）
A.the exhaust valves B.the fuel valves C.indicator cocks D.the fuel pumps
单项选择题 In each cylinder cover is a large central opening for mounting （）
单项选择题 In an ordinary four-stroke engine the exhaust valves open （）
单项选择题 In an ordinary diesel engine the fuel injection begins （）
