For three low density gases A, B, C pressure versus temperature...

In case of constant volume process, i.e., isochoric process, 

From ideal gas equation,

$\dfrac{P}{T} = n\dfrac{R}{V} =$constant

Or we have, $P = \dfrac{nR}{V}\left(t + 273\right)$

If $P = 0 ⇒ t = - 273 ° C$

Thus, when temperature goes to $- 273 ° C$, all constituent particles get freezed and pressure goes to zero irrespective of the density of gas.

Hence, the temperature corresponding to the point $K = - 273 ° C$.