In a closed-loop process control system, what is meant by the integral mode of control?

Correct Answer: Option D — It is a control mode that produces a control action that is proportional to the accumulation of error over time.

Integral control mode, or 'reset,' produces an output proportional to the magnitude and duration of the error signal. By accumulating the error over time, this mode eliminates steady-state offset, ensuring the controlled variable eventually reaches the exact set point, even in the presence of sustained load changes.