Explanation

(d)
Urea is one of the most important fertilizer as it does not change pH of soil. Urea, after hydrolysis gives ammonia and $CO_{2}$. Ammonia is taken up by plants leaving behind $CO_{2}$.$CO_{2}$ is a very weak acidic oxide. It doesn’t affect pH of soil
$NH_{2}CONH_{2}\overset{\ \ \ \ H_{2}O\ \ \ \ }{\rightarrow}2NH_{3} + CO_{2}$
urea