Why is there a centripetal acceleration if the velocity does not increase?

a. Velocity changes direction as you move around the circle, causing a Δv
b. Velocity in a circle is always constant
c. Because gravity will hold any object in a circular motion

I am almost sure its not "b" but I don't know about the others. Please explain in very simple easy to understand terms. Thanks!

centripetal acceleration occurs when velocity changes direction.