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

1. A \(\begin{array}{l}
   {\sigma _1}\, \ne \,0,\,\,{Q_1}\, = \,0\\
   {\sigma _2}\, = \,0,\,\,{Q_2}\, = \,0
   \end{array}\)
2. B \(\begin{array}{l}
   {\sigma _1}\, \ne \,0,\,\,{Q_1}\, = \,0\\
   {\sigma _2}\, \ne \,0,\,\,{Q_2}\, = \,0
   \end{array}\)
3. C \(\begin{array}{l}
   {\sigma _1}\, = \,0,\,\,{Q_1}\, = \,0\\
   {\sigma _2}\, = \,0,\,\,{Q_2}\, = \,0
   \end{array}\)
4. D \(\begin{array}{l}
   {\sigma _1}\, \ne \,0,\,\,{Q_1}\, \ne \,0\\
   {\sigma _2}\, \ne \,0,\,\,{Q_2}\, \ne \,0
   \end{array}\)