For how many of the following the weight increases in the applied magnetic field. 

${\mathrm{O}}_2, \mathrm{NO}, {\mathrm{CuSO}}_4,\hspace{0.17em}{\mathrm{ZnSO}}_4, {\mathrm{MnSO}}_4$

It is observed that an increase in weight observe when paramagnetic substance are placed in the magnetic field. All the given compounds are paramagnetic except ${\mathrm{ZnSO}}_4$ because it is diamagnetic. Therefore, except ${\mathrm{ZnSO}}_4$ rest of the compounds experience an increase in weight when placed in a magnetic field.