The correct order of normal boiling points of ${\mathrm{O}}_2,{\mathrm{N}}_2 {\mathrm{NH}}_3$ and ${\mathrm{CH}}_4$ for whom the values of van der Waal's constant 'a' are 1.360, 1.390, 4.170 and 2.253 ${\mathrm{L}}^2 \mathrm{atm} {\mathrm{mol}}^{-2}$ respectively, is ;

The proper sequence of the normal boiling temperatures  ${\mathrm{O}}_2,{\mathrm{N}}_2 {\mathrm{NH}}_3$ and ${\mathrm{CH}}_4$ is ${\mathrm{O}}_2<{\mathrm{N}}_2<{\mathrm{CH}}_4<{\mathrm{NH}}_3$

(for which the values of vander waals constant 'a' are 1.360, 1.390, 4.170, and   2.253 ${\mathrm{L}}^2 \mathrm{atm} {\mathrm{mol}}^{-2}$ 

a is an indirect indicator of the strength of the molecules' attractive forces, the boiling point will increase as the van der Waals constant, or a, increases in value.

So, option B is correct answer.