The Nyquist plot of a stable transfer function $G(s)$ is shown in the figure. We are interested in the stability of the closed loop system in the feedback configuration shown.
Which of the following statements is true?
- $G(s)$ is an all-pass filter
- $G(s)$ has a zero in the right-half plane
- $G(s)$ is the impedance of a passive network
- $G(s)$ is marginally stable