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.    

answer; /// i believe that the correct answer is (50%);

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.