A material is described by the following electrical parameters as a frequency of $10 \; \mathrm{GHz}, \sigma=10^{6} \mathrm{mho} / \mathrm{m}, \mu=\mu^{0}$ and $\sigma / \sigma^{0}=10$. The material at this frequency is considered to be
\[\left(\sigma_{0}=\frac{1}{36 \pi} \times 10^{-9} \mathrm{~F} / \mathrm{m}\right)\]
- a good conductor
- a good dielectric
- neither a good conductor, nor a good dielectric
- a good magnetic material