a b c d

d

$\text{Resolving Component of T }$ $ T cos\theta = mg $ ............(1) $ T sin\theta = qE = q\frac{\sigma}{\epsilon_0}$ .............(2) $\text{Dividing equation (1)( and (2),we get}$ $ tan\theta = \frac{q\sigma}{mg\epsilon_0}$ $\Rightarrow \sigma \propto tan\theta $