A small ball of mass m and charge +q tied with a string of length l , rotating in a vertical circle under gravity and a uniform horizontal electric field E as shown . The tension in the string will be minimum for

Question

$(a)\;\theta=tan^{-1} (\large\frac{qE}{mg})\qquad(b)\;\theta=\pi\qquad(c)\;\theta=0^{0}\qquad(d)\;\theta=\pi+tan^{-1} (\large\frac{qE}{mg})$