单项选择题
Vents are led from the engine to the head tank for the release of （） from the cooling water.
A.air B.heat C.sludge D.steam
单项选择题 Vents are led from the engine to head tank （） from the cooling water.
单项选择题 Vee-type engines have the connecting rods from two cylinders connected to each （） of the crankshaft.
单项选择题 Valve overlap is the period during which （）.
