Nitrogen availability is often a limiting factor in plant growth. nitrogen tends to be scarce because
a) fossil fuel combustion uses the available nitrogen; what is left for the plants is not enough, making the fuel combustion a limiting factor.
b) decomposers are unable to recycle nitrogen, meaning that all nitrogen used must be produced by bacteria.
c) there is very little nitrogen present in the atmosphere.
d) nitrogen gas (n2) is so stable that only a few organisms are capable of turning it into nitrogen that can be used for living things.

D) Nitrogen gas (N2) is so stable that only a few organisms are capable of turning it into nitrogen that can be used for living things.

Explanation:

Nitrogen cycle is very important for the growth and development of the plants. This is because of the fact that nitrogen being in the form of nitrogen gas in the atmosphere cannot be absorbed by the plants readily instead it should be converted into forms which can be utilized by the plants. Only few organisms particularly some strains of bacteria can perform the task of nitrogen fixation in the soil.    

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

characterization of nanoparticles is a critical step in nanomaterial production as it provides information of dimension, morphology, surface charge, distribution and degree of surface functionalization.