The correct answer is: D. discontinuous
An on-off controller is a type of control system that switches between two states, on and off, in response to a signal. This type of controller is often used in simple systems where a high degree of accuracy is not required.
A digital system is a system that uses discrete values to represent information. This type of system is often used in computers and other electronic devices.
A linear system is a system in which the output is proportional to the input. This type of system is often used in physics and engineering.
A nonlinear system is a system in which the output is not proportional to the input. This type of system is often used in biology and economics.
A discontinuous system is a system in which the output changes abruptly from one value to another. This type of system is often used in control systems.
In the case of an on-off controller, the output is either on or off. There is no in-between state. This means that the system is discontinuous.