单项选择题
In each cylinder cover is a large central opening for mounting （）
A.the indicating cock B.the starting valve C.air inlet valve D.the exhaust valve
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 （）
单项选择题 In an oil cooler circulated by sea water, the oil is at a larger pressure, the result being that any leak in the cooler will mean a loss of （）.
