Which of the following expressions correctly defines the Van't Hoff factor $i$?

One molal solution of a carboxylic acid in benzene shows the elevation of boiling point of $1.518 \ K$. The degree of association for dimerization of the acid in benzene is $........ \%$. ($K_b$ for benzene $= 2.53 \ K \ kg \ mol^{-1}$)

Molecules of benzoic acid $(C_6H_5COOH)$ dimerise in benzene. '$w$' $g$ of the acid dissolved in $30 \ g$ of benzene shows a depression in freezing point equal to $2 \ K.$ If the percentage association of the acid to form dimer in the solution is $80,$ then $w$ is : ............. $g$
(Given that $K_f = 5 \ K \ kg \ mol^{-1},$ Molar mass of benzoic acid $= 122 \ g \ mol^{-1}$ )

The molecular weight of benzoic acid dissolved in benzene is found to be ............ $g/mol$.

The experimental depression in freezing point of a dilute solution is $0.025 \ K$. If the van't Hoff factor $(i)$ is $2.0$, the calculated depression in freezing point (in $K$) is

In a solvent,$50\,\%$ of an acid $HA$ dimerizes and the rest dissociates. The van't Hoff factor of the acid is $.....\times 10^{-2}$. (Round off to the nearest integer)