The necessary and sufficient condition for a rational function of $\mathrm{s}$. $\mathrm{T}(\mathrm{s})$ to be driving point impedance of an $\text{RC}$ network is that all poles and zeros should be
- simple and lie on the negative axis in the $s$-plane
- complex and lie in the left half of the $s$-plane
- complex and lie in the right half of the $s$-plane
- simple and lie on the positive real axis of the $s$-plane