The nitrogen cycle .
A. indicates the process of uptake of nitrates (NO₃ minus) by plants.
B. marks transformation of ammonium (NH₄ plus) into nitrites (NO₂ minus) by bacteria.
C. marks synthesis of ammonium (NH₄ plus) by decomposers.
D. marks transformation of nitrogen (N₂) from the atmosphere to ammonium (NH₄ plus) by bacteria.
E. marks organisms that take part in transformation of nitrogen from the atmosphere (N₂) into ammonium (NH₄ plus) and are located in the root nodules.

D. marks transformation of nitrogen (N₂) from the atmosphere to ammonium (NH₄ plus) by bacteria.

Explanation:

The nitrogen cycle is a biogeochemical cycle which involves transformation of atmoshperic nitrogen into many chemical forms including nitrite (NO2), nitrates (NO3) and ammonium (NH4).

The process of nitrogen cycle starts with the process of nitrogen fixation. In this process several nitrogen fixation bacteria such as cyno bacteria converts the atmospheric nitrogen into ammonium (NH4) in the soil. The resultant ammonium (NH4) can be directly used by plants or transform into nitrites or nitrates through nitrification process.

Hence, the correct option is D.

hydroxyl -oh

alcohols, always polar, can form hydrogen bonds with h2o molecules

carboxyl -cooh  

cargoxylic acids, has acidic properties which is a source of hydrogen ions, found in cells in ionized for with a charge of oh-1

carbonyl > co

ketone if within skeleton, aldehyde if group is at the end of skeleton, k & a may be structural isomers, it determines 2 sugars (ketose & aldose)

amino -nh2

amines, acts as a base, it can pick up h+ ions from surrounding solution, ionized with charge of 1+

methyl ch2

addition to rna/dna affects and gene expression

phosphate -opo3 ²⁻

organic phosphates, contributes to negative charge to, molecule that it is a part of, and potential to react with h20

sulfhydryl -sh

thiols, cross-linking stabilize the protein, and it is structure