The correct option is D nitrification
∙ Nitrification is the process of conversion of ammonia into nitrite and then nitrates.
∙ Denitrification is the conversion of nitrogenous compounds into gaseous nitrogen.
∙ Release of ammonia through decomposition of dead bodies and
excretory wastes of organisms is known as ammonification.
∙ Combustion is the process where a substance burns in the presence of oxygen, giving off heat and light in the process.