Which of the following best describes an example of a specific immune response to pathogens?
a: cytotoxic t cells are activated and destroy cells that pathogens have invaded.
b: fever increases body temperature and speeds up the body's reaction to pathogens.
c: phagocytes identify cells invaded by pathogens and mark them for destruction.
d: mucus traps pathogens and destroys them before they can enter the body.

The answer is A:Cytotoxic T cells are activated and destroy cells that pathogens have invaded.
A specific immune response is antigen-dependent while a non-specific immune response is antigen-independent. The non-specific immunity is also called innate immunity. The examples of the non-specific immunity are fever (choice B), phagocytosis by macrophages (choice C), and skin and mucus (choice D).Cytotoxic T-cells are an example of the specific immune response. These cells recognize antigens on infected cells and kill them before the infection could spread.