How many of the following are diamagnetic?

${\mathrm{O}}_2,{\mathrm{O}}_2^{2+},{\mathrm{O}}_2^{2-},{\mathrm{B}}_2^{2-},{\mathrm{C}}_2^{2+},{\mathrm{C}}_2^{2-},{\mathrm{C}}_2,{\mathrm{N}}_2,{\mathrm{N}}_2^{+}$

The molecules have a diamagnetic character if they have paired electrons. So, 

${\mathrm{O}}_2^{2+},{\mathrm{O}}_2^{2-},{\mathrm{B}}_2^{2-},{\mathrm{C}}_2^{2-},{\mathrm{C}}_2$, are the molecule which is diamagnetic.