单项选择题 The oil lubricating diesel engine cylinders usually contain additives formulated to impart a high degree of alkalinity to （） the acid conditions.

单项选择题 The oil is drawn from a drain tank through （）, one of a pair of pumps, into one of fine filters.

单项选择题 The needle valve will open when the fuel pressure acting on the needle valve （） exerts a sufficient force to overcome the spring compression.