Correct Response: B. Acquired immunity is a specific immune response that is generated after exposure to specific antigens. Each lymphocyte contains receptors that recognize a single antigen. When that specific antigen binds to a receptor on a lymphocyte, the lymphocyte divides to produce many cells capable of recognizing and attacking the pathogen source of the antigen. After the initial stimulation of a lymphocyte, the body can respond more rapidly upon exposure to the same pathogen. Immune responses as a result of increased body temperature (A) and natural killer cells (C) are part of the non-specific immune response, rather than acquired immunity. Although certain phagocytes help trigger clonal selection by presenting antigens to lymphocytes, phagocytes (D) are themselves part of the non-specific immune response, in that they recognize and destroy pathogens indiscriminately.
