If angular acceleration is constant, then angular velocity must be:

When angular acceleration is constant, it means that the rate of change of angular velocity is uniform over time. This leads to the situation where angular velocity must either be increasing or decreasing depending on the sign of the angular acceleration. If the angular acceleration is positive, the angular velocity will increase over time; conversely, if the angular acceleration is negative, the angular velocity will decrease. The key point here is that constant angular acceleration does not imply that angular velocity is constant or zero; instead, it suggests a continuous change in angular velocity in one direction or another.

Therefore, the correct answer accurately reflects the relationship between constant angular acceleration and angular velocity, highlighting that angular velocity will either increase or decrease as a result of the uniform change indicated by the constant angular acceleration.