(单选题)
Because the top of the connecting rod swings about the pin and changes direction each time the piston reaches mid-stroke, the relative speed between bearing and pin at mid-stroke is zero, ()to a maximum as the piston approaches top or bottom dead center and then () back to zero again as the piston approaches mid-stroke and the connecting rod changes direction.
Aaccelerates;decelerates
Baccelerates;accelerates
Cdecelerates;decelerates
Ddecelerates;accelerates
正确答案
答案解析
略