Explanation

(d)
In Kjeldahl’s method, the nitrogen is quantitatively converted into ammonia by heating with NaOH
$C + H + N\overset{\ \ \mathrm{\Delta}\ \ }{\rightarrow}\left( NH_{4} \right)SO_{4} + CO_{2} + H_{2}O$
(from organic compound)
$\left( NH_{4} \right)_{2}SO_{4} + 2NaOH \rightarrow Na_{2}SO_{4} + 2NH_{3} + 2H_{2}O$
In Dumas method nitrogen present in organic compound is quantitatively converted into $N_{2}.$