Select the best description of the negative selection process of lymphocyte maturation.
A) teaching a lymphocyte to recognize "self" from foreign antigens
B) removal of lymphocytes that react with "self" cells
C) removal of lymphocytes that fail to recognize "self" cells
D) allowing the survival of lymphocytes that cannot bind to MHC proteins

B) removal of lymphocytes that react with "self" cells

Explanation:

By negative selection, we mean to say that the lymphocytes which are reacting with self cells too strongly must undergo apoptosis otherwise they will cause auto-immunity which will lead to destruction of self cells.

Before negative selection, the naive lymphocytes undergo positive selection during which they are allowed to interact with MHC-I or MHC-II. This kind of selection is necessary so as to ensure that the selected lymphocytes have affinity towards MHC molecule for generation of effective immune response whenever it is required. All those cells that do not recognize self antigen undergo apoptosis because they are useless and the lymphocytes which recognize MHC moderately are selected for the next stage which is negative selection.

Once these lymphocytes have passed test for positive selection, they have to undergo test for negative selection. All those lymphocytes which are interacting very strongly with self antigen are rejected and finally undergo apoptosis.

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.