(c) Oxygen is paramagnetic due to the presence of two unpaired electron :

${O_2} = \sigma {(1s)^2}{\sigma ^ * }{(1s)^2}\sigma {(2s)^2}{\sigma ^ * }{(2s)^2}$ $\sigma {(2{p_x})^2}\pi {(2{p_y})^2}\pi {(2{p_x})^2}{\pi ^ * }{(2{p_y})^1}{\pi ^ * }{(2{p_z})^1}$