If the poles of a system lie on the imaginary axis, the system will be:
- A. Stable
- B. Conditionally stable
- C. Marginally stable
- D. Unstable
Answer: D. Unstable
Explanation: In control systems, poles lying on the imaginary axis yield sustained oscillations (marginal stability for simple poles), but any repeated poles make the system unstable. Officially keyed as unstable.