Shown in the figure are two point charges $+Q$ and $-Q$ inside the cavity of a spherical shell. The charges are kept near the surface of the cavity on opposite sides of the centre of the shell. If $\sigma_1$ is the surface charge on the inner surface and $Q_1$ net charge on it and $\sigma_2$ the surface charge on the outer surface and $Q_2$ net charge on it then : <br>

Question

( A ) $\sigma_1 \neq 0,\; Q_1 = 0$
$\sigma_2 = 0, \; Q_2 = 0$
( B ) $\sigma_1 \neq 0, \; Q_1 = 0$ $\sigma_2 \neq 0, Q_2 = 0$
( C ) $\sigma_1 \neq 0, \; Q_1 \neq 0$ $\sigma_2 \neq 0, Q_2 \neq 0$
( D ) $\sigma_1 = 0, \; Q_1 = 0$ $\sigma_2 = 0, Q_2 = 0$