Nitrite is converted to nitrate by

Which of the following is true for nitrogen fixation?

What is the function of denitrifying bacteria?

One of the ways in which the nitrogen of the atmosphere is converted into nitrate for plants is by the action of

Match the organisms given in Column $I$ to their functions given in Column $II$ and choose the correct option.

Column $I$	Column $II$
$A$. Thiobacillus	$1$. Free-living nitrogen-fixing cyanobacteria
$B$. Nitrosomonas	$2$. Denitrification
$C$. Nostoc	$3$. Free-living aerobic nitrogen-fixing bacteria
$D$. Azotobacter	$4$. $NH_{3}$ to Nitrite

Codes:
$A \quad B \quad C \quad D$

Describe the Nitrogen Cycle.