The value of van der waal's constant 'a' for the gases $O_2,N_2,N{H}_3$ are $1.360,1.390,4.170$ $L^{2}atmmo{l}^{-2}$ respectively. The gas which can most easily be liquified is

The correct option is C $N{H}_3$
More the value of 'a' more will be the pressure correction term $\frac{a{n}^2}{V^2}$ . More the value of pressure correction term implies that more will be the interaction and more easy will be the liquification.