单项选择题
A.the piston is just coming upward from the bottom dead center
B.the piston has moved about one-fifth of the way up
C.the piston has moved most of the way up and almost reached the TDC
D.the piston has just past the TDC
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 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（）