The correct answer is D. All of the above.
Angular acceleration is the rate of change of angular velocity. It is a vector quantity, with magnitude and direction. The magnitude of angular acceleration is denoted by $\alpha$ and is measured in radians per second squared (rad/s$^2$). The direction of angular acceleration is along the axis of rotation, and is given by the right-hand rule.
Angular acceleration can be expressed in a number of different ways, including radians per second squared (rad/s$^2$), degrees per second squared (deg/s$^2$), and revolutions per second squared (rev/s$^2$).
- Radians per second squared (rad/s$^2$) is the most common unit of angular acceleration. It is defined as the rate of change of angular velocity in radians per second.
- Degrees per second squared (deg/s$^2$) is another common unit of angular acceleration. It is defined as the rate of change of angular velocity in degrees per second.
- Revolutions per second squared (rev/s$^2$) is a less common unit of angular acceleration. It is defined as the rate of change of angular velocity in revolutions per second.
The choice of units depends on the specific application. For example, if you are studying the motion of a wheel, you might use rad/s$^2$. If you are studying the motion of a planet, you might use deg/s$^2$.
In conclusion, angular acceleration can be expressed in a number of different ways, including radians per second squared (rad/s$^2$), degrees per second squared (deg/s$^2$), and revolutions per second squared (rev/s$^2$). The choice of units depends on the specific application.