ANS:D - all the above.

1. Radians per second squared (rad/s²): This is the standard unit for expressing angular acceleration. It represents the change in angular velocity per unit time, where angular velocity is measured in radians per second. Radians are a natural unit for angular measurement because they directly relate to the arc length on a circle. Angular acceleration measured in radians per second squared is widely used in physics and engineering, particularly in calculations involving rotational motion.
2. Degrees per second squared (deg/s²): While radians per second squared is the standard unit, angular acceleration can also be expressed in degrees per second squared. However, radians are generally preferred because they are mathematically more convenient, especially when dealing with trigonometric functions. Nevertheless, degrees are commonly used in certain contexts, particularly in everyday measurements and less technical discussions.
3. Revolutions per second (rev/s): This unit does not represent angular acceleration but rather angular velocity. Revolutions per second denote the number of complete revolutions an object makes in one second. It's a measure of how fast an object is rotating, not how quickly its rotation is changing, which is the essence of angular acceleration.