Which control action can never be used alone?

For type 0 system the starting point (i.e. ω = 0) of polar plot is finite and is on positive real axis.

If poles lie in first quadrant, damping ratio is

The phase difference (jω - p₁) means

Assertion (A): The phase angle plot in Bode diagram is not affected by change in system gain.

Reason (R): The variation in gain has no effect on phase margin of the system.