Is based on recognition of antigens that are specific to a pathogen is the first, and most general, mechanism of protection against pathogens is found only in vertebrates depends on an infected animal's previous exposure to a pathogen

The question is incomplete. The complete question is:

Question: Innate immunity:

a) is based on recognition of antigens that are specific to a pathogen.

b) is the first and most general, mechanism of protection against pathogens

c) is found only in vertebrates

d) depends on an infected animal's previous exposure to a pathogen

b) is the first and most general, mechanism of protection against pathogens

Explanation:

Innate immunity is the nonspecific immune response that provides immediate and the most general protection against all types of pathogens, parasites, toxins and cancer cells. Innate immune responses serve to prevent the pathogens from entering the body. The components of innate immunity also rapidly destroy those pathogens that have entered the body.

Some of the components of innate immunity are the first line of defense such as the physical and chemical barriers of the skin and mucous membranes. The components of the second line of defense such as natural killer cells, phagocytes and inflammatory response are also involved in innate immune responses.

For example, cuticle or skin serves as a physical barrier to pathogens that come in contact with an animal’s body. Phagocytosis kills the bacteria that invade 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).