A:Warning; following
B:Having warned; following
C:Having been warned; following
D:Warned; followed
热机的四个冲程中,将内能转化为机械能的是( )
用同样大小的力F,分别以图所示的方式依次作用在同一木箱上,使木箱向右运动,其中滑动摩擦力最小的是()