[单选题]
Under what condition is ak*qu kzf.-ai,o+ gd :tverage velocity equal to the average of the obje)qh kzmsqo/nyf( d6-.ct's initial ad)/- (z y6o. qmshqknfnd final velocity?
A. The acceleration must be constantly changing.
B. The acceleration must be constant.
C. This can only occur if there is no acceleration.
D. This is impossible.