A wheel having mass m has charges +q and -q on diametrically opposite points. It remains in equilibrium on a rough inclined plane in the presence of a vertical electric field E. Then value of E is :

A

$$\frac{mg \tan \theta}{q}$$

B

$$\frac{mg}{q}$$

C

$$\frac{mg}{2q}$$

D

$$\frac{mg \tan \theta}{2q}$$