Which is only active during a specific immune response?
a. neutrophils
b. macrophages
c. lysozymes
d. t cells

Ans. (D). T cells.

Immune responses are reactions of immune cells and substances against foreign substances or abnormal cells.

Specific immune responses are elicited by adaptive immune system, which is made up of T-lymphocytes and B-lymphocytes. These cells are highly specialized that function in elimination of pathogens and prevent their growth.

Thus, the correct answer is option (D).

weathering is the answer.

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).