A system consists of a uniform charged sphere of radius R and a surrounding medium filled by a charge with the volume density \[\rho =\frac{\alpha }{r},\] where \[\alpha \]a positive constant is and r is the distance from the center of the charge. The charge of the sphere for which the electric field intensity E outside the sphere is independent of r is-

• A. \[\pi {{R}^{2}}\alpha \]           
• B. \[4\pi {{R}^{2}}\alpha \]
• C. \[2\pi {{R}^{2}}\alpha \]          
• D.        \[3\pi {{R}^{2}}\alpha /4\]