[单选题]
Under what condition p/fb;h+5 mwv dyt e;a0.ebg 9.hyu8 -fpy2 eceis average velocity equal to the average of the object's initial-u ee2peh fy.y bgc98. and 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.