[单选题]
Under what condition is average velocity equal to the average of the object'snl)(g6 hp hgbst, 32uu ix6(oc6:l xu,g3n ggbc nitial and finalx: g66uncx ,gl c3gbo( 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.