Which compound is formed by heating with nitric acid in the estimation of phosphorus in the Carius method?

Match column $-I$ and column $-II$ with the correct relation:

Column $-I$	Column $-II$
$(i)$ Dumas method	$(a)$ Absorption of $NH_3$ in $H_2SO_4$
$(ii)$ Kjeldahl's method	$(b)$ $BaCl_2$ by added $BaSO_4$
$(iii)$ Carius method	$(c)$ Mixture of Magnesia
$(iv)$ Estimation of phosphorus	$(d)$ $N_2$

What is the formula for calculating the percentage of nitrogen in the Dumas method?

In which of the following compounds is the Kjeldahl method applicable?

In Kjeldahl's method for the estimation of nitrogen,the formula used is

$0.25 \ g$ of an organic compound $A$ containing carbon,hydrogen,and oxygen was analysed using the combustion method. The increase in mass of the $CaCl_2$ tube and the potash bulb at the end of the experiment was found to be $0.15 \ g$ and $0.1837 \ g$,respectively. The percentage of oxygen in compound $A$ is $.... \%$. (Nearest integer)
(Given: molar mass in $g \ mol^{-1}$,$H: 1, C: 12, O: 16$)