How Does an Object Moving in a Circle at Constant Speed Accelerate?

[wobba63]

Homework Statement

Acceleration is a vector representing the rate of change of velocity. An object moving in a circle at constant speed:

A. accelerates without changing its velocity
B. Has constant acceleration
C. Changes speed but not velocity
D. Changes velocity but not speed

Homework Equations

A_rad=V²/R

The Attempt at a Solution

The answer given in my book is D, which makes sense, but I also don't see how B is wrong. If the object's speed is constant, and radial acceleration is based off the magnitude of velocity (hence changing direction of velocity doesn't affect it), then shouldn't the acceleration also be constant?

 

[tms]

Remember that acceleration is a vector; it has a direction.