Chapter 10 - Section 10.1 - Angular Velocity and Acceleration - Got It? - Page 171: 10.1

c)

Since tangential acceleration is equal to $\alpha r$, we know that a constant angular acceleration means that there is a constant tangential acceleration. The only tangential acceleration that is constant is c). In addition, because radial acceleration equals $\frac{v^2}{r}$, when the velocity increases at a tangential rate, $a_r$ increases at an exponential rate.