IMMUNOLOGY

Detailed explanation-1: -Once the immune system identifies an invader, draining lymph nodes recruit infection-fighting T-cells within 24 hours. During the next week or so, the T-cells proliferate and induce B-cells to produce antibodies specific to the invader.

Detailed explanation-2: -From the given choices, option (b) best describes the function of a lymph node. The major function of a lymph node is to expose the pathogens to the specialized leukocytes known as the lymphocytes. The lymph nodes filter the lymph and remove the pathogens which are then exposed to the lymphocytes.