单项选择题
A.a two-stroke engine can’t work without cylinders
B.a two-stroke engine can’t work without pistons
C.a two-stroke engine can’t work without crankshafts
D.a two-stroke engine can’t work without a blower
单项选择题 One of the differences between a two-stroke engine and a four-stroke engine is,（）
单项选择题 In a diesel engine,（） works as working medium and changes the heat energy to mechanical energy, changes the reciprocating movement to rotary moment（）
单项选择题 In a diesel engine, offers the heat energy directly（）； works as working medium and changes the heat energy to mechanical energy（）