Which one is not correct mathematical equation for Dalton's Law of partial pressure? Here $p=$ total pressure of gaseous mixture.

1. A
   $p=p_1+p_2+p_3$
2. B
   $p=n_1\frac{RT}{V}+n_2\frac{RT}{V}+n_3\frac{RT}{V}$
3. C
   $p_i={\chi }_{i}p$, where $p_i=$ partial pressure of $i^{th}$ gas; ${\chi }_i=$ mole fraction of $i^{th}$ gas
4. D
   $p_i={\chi }_i{p}_i^{\circ }$, where ${\chi }_i=$ mole fraction of $i^{th}$ gas and $p_i^{\circ }=$ pressure of $i^{th}$ gas in pure state