A PI controller is implemented in a system with unity negative feedback. What is the primary role of the integral action in a PI controller?

Correct option is B

​$$\text{In a PI controller, the integral (I) action integrates the error over time:} \\[8pt]u_I(t) = K_I \int e(t)\, dt \\[10pt]\textbf{Primary role of integral action:} \\[6pt]\bullet \ \text{Accumulates past errors} \\[4pt]\bullet \ \text{Forces the steady-state error to zero (for step inputs)} \\[4pt]\bullet \ \text{Compensates for constant disturbances and biases}$$​​