Which one of the following steps would be included in the primary response in humoral immunity?
a. antigen binds to antibodies
b. cytotoxic t cells bind to infected body cells and destroy them
c. t cells activate cytotoxic t cells
d. a macrophage consumes a virus and displays antigens on its surface and signals t cells to divide.

The primary immune response in humoral immunity, when we're talking about our body's natural defence capabilities against harmful foreign or domestic invaders would be when a macrophage consumes a virus and displays antigens on its surface and signals helper T cells to divide - D. This is usually our first line of defence found on the spot.