单项选择题 The needle valve in the injector （） at a pre-set pressure which ensures that the fuel will atomize once it enters the cylinder.

单项选择题 The needle valve in a fuel valve will （） when the fuel pressure action on the needle valve tapered face exerts a force lower than that of the spring compression.

单项选择题 The most common cause of lowering the crankcase lube oil flash point is （）.