Which of the following is an example of a nonspecific immune response? a. the receptors of a b lymphocyte bind to an antigen. b. a t lymphocyte attacks and destroys a cancer cell. c. a plasma cell releases antibodies. d. a macrophage engulfs invading bacteria.

The correct answer is D. A macrophage engulfs invading bacteria.
Non-specific immune response (or innate immune response) includes mechanisms that defend the host from infection by pathogen by recognizing and responding to pathogens but without providing long-lasting immunity to the host. Mechanisms of this respond include recruiting immune cells to sites of infection via cytokines, identification and removal of foreign substances by white blood cells (like macrophages, neutrophils), activation of the adaptive immune system (antigen presentation).