Which of these is not one of the structures considered to be the immune system's first line of defense? a) skin b) mucous membranes c) b cells d) tears

The B cells are not considered as first line defense structures of the immune’s system

Option C

Explanation:

Our body is protected internally by nature by many layers of defense. Any microbe or a foreign material that disturbs the body is defended by these barriers.

The first layer of defense required physical and chemical barrier such as the skin, mucous membrane, tears, saliva etc . The second line defense system involves the cells and the tissues that protect the body.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).