Arrange the following steps in the process of adaptive immunity from initial exposure to a pathogen to the formation of memory cells: A. Activation of T cells, B. Antigen presentation by dendritic cells, C. Proliferation of B cells and antibody production, D. Formation of memory cells.

The process starts when dendritic cells pick up the pathogen’s antigens and present them to the immune system, so step B comes first. Then those antigens activate T cells, which is step A. Activated T cells help B cells multiply and produce antibodies, which is step C. Finally, some of the cells become long‑lasting memory cells, step D. This sequence—from antigen capture to T cell activation, B cell response, and memory formation—lets the body remember how to fight the same pathogen later.