Consider the following liquid – vapour equilibrium: $\text{Liquid}\rightleftharpoons \text{Vapour}$. Which of the following relations is correct?

1. A
   $\frac{d\ln P}{dT}=\frac{-\Delta H_v}{RT}$
2. B
   $\frac{d\ln P}{d{T}^2}=\frac{-\Delta H_v}{T^2}$
3. C
   $\frac{d\ln P}{dT}=\frac{\Delta H_v}{R{T}^2}$
4. D
   $\frac{d\ln G}{d{T}^2}=\frac{\Delta H_v}{R{T}^2}$