First we shall look at some terms:
Velocity - frequency of change of an objects position.
Acceleration - frequency of change of an objects velocity
Since velocity covers both change in direction and speed, we can asume that the answer is B, not because it's the only one we worked with, but because the others don't make any sense:
A - this is not correct, because a chnage in direction can be done withough a change in speed.
C - The scientific definition of acceleration does include speed, and this is not a reasonable answer.
D - Velocity can change, unlike said in the sentence.
Hope it helped,
BioTeacher101