Which one of the following molecules is paramagnetic?

Solution :
The molecular orbital configuration of the molecules given is
Total no. of electrons in $$NO = 7\left( N \right) + 8\left( O \right) = 15$$
Hence $$E.C.$$  of $$NO$$
$$\eqalign{ & = KK\sigma {\left( {2s} \right)^2}{\sigma ^ * }{\left( {2s} \right)^2}\sigma {\left( {2{p_z}} \right)^2} \cr & \pi {\left( {2{p_x}} \right)^2} = \pi {\left( {2{p_y}} \right)^2}{\pi ^ * }{\left( {2{p_x}} \right)^1} \cr & = \pi * {\left( {2{p_y}} \right)^o} \cr} $$
Due to presence of one unpaired electron $$NO$$  is paramagnetic.
Except $$NO$$  all are diamagnetic due to absence of unpaired electrons.