Which parameter supplies energy or material to the process to regulate the deviation of a process output?

The manipulated variable is the correct choice because it directly influences the process by altering the conditions to achieve the desired output. In control systems, the manipulated variable is the parameter that is actively changed or adjusted by the operator or the control system itself in response to feedback. Its primary role is to supply energy or material to the process, thereby regulating how the controlled variable (the actual output of the process) deviates from the setpoint or desired value.

For instance, in a temperature control system, the manipulated variable might be the flow of steam or coolant to a reactor. By adjusting this flow, the system can counteract any deviations in temperature (controlled variable) from the desired level. This dynamic interaction makes the manipulated variable essential in maintaining optimal process conditions.