In an insulated cable having core diameter d and overall diameter D, the ratio of maximum to minimum dielectric stress is given by

A

$$\left(\frac{D}{d}\right)^{\frac{1}{2}}$$

B

$$\left(\frac{D}{d}\right)^2$$

C

$$\left(\frac{D}{d}\right)$$

D

$$\left(\frac{d}{D}\right)$$