Fishing and Guano birds assist the cycling of

The process of conversion of $2 NO_{3}^{-} \rightarrow 2 NO_{2}^{-} \rightarrow 2 NO \rightarrow N_{2}O \rightarrow N_{2}$ is called and is carried out by:

The conversion of nitrate to nitrous oxide and nitrogen gas is termed as

Identify $X$ and $Y$ in the given nitrogen cycle chart.

The nature of $Bacillus \ rimosus$ is:

Choose the correct pair:

Column-$I$	Column-$II$
$I$. Nitrosomonas	Nitrite to nitrate
$II$. Thiobacillus	Denitrification
$III$. Nostoc	Free-living nitrogen fixer
$IV$. Azotobacter	Anaerobic nitrogen fixer