What process control system control mode is most likely to have steady-state error (also known as offset or residual error)?

Correct Answer: Option A — Proportional mode

Proportional control mode relies on the error signal to generate an output. Because the output is directly proportional to the error, the system requires a non-zero error to maintain a steady-state output, which inherently results in a residual offset or steady-state error between the setpoint and process variable.