Final answer:
Among the WBCs listed, NK cells, cytotoxic T cells, helper T cells, and B cells are all types of lymphocytes. The remaining option, M cells, are NOT lymphocytes.
Step-by-step explanation:
White blood cells (WBCs), or leukocytes, are an essential component of the immune system, with different types playing various roles in protecting the body against infection. Among the different types of WBCs are lymphocytes, which include natural killer cells (NK cells), B cells, and different subsets of T cells such as cytotoxic T cells, helper T cells, and suppressor T cells.
To answer the question, which of the following WBCs are NOT lymphocytes: NK cells, M cells, cytotoxic T cells, helper T cells, B cells; we must identify cells that are not part of this trio of major lymphocyte groups. NK cells, cytotoxic T cells, helper T cells, and B cells are all types of lymphocytes. Therefore, out of the options given, the M cells are NOT lymphocytes.