单项选择题 The shells are secured by means of bearing caps and studs, the necessary clearance being provided by means of （） of different thickness.

单项选择题 The sequence of parts in a generally used fuel oil supply system for a main engine is （） (1)tanks in the double bottom (2)centrifuges (3)service tank (4)settling tank (5)viscosity regulator

单项选择题 The sequence of fuel injection into cylinders is determined by （）.