(a) (10%) Explain why a lag compensator (e.g., a PI controller) can NEVER stabilize G.

Question 1.(20%、5% for each sketch)The pole/zero plots of four transfer functions G1(s) to G4(s) are shown in Figure 1. Sketch the step response of each transfer function. On your sketches, you should show important details of the responses. such as the overshoot, undershoot, steady state, etc. if any. Missing any important detail will result in mark deduction.