Final answer:
T cells (T lymphocytes) are the white blood cells responsible for the adaptive immunity that targets and destroys specific pathogens, making them the correct answer (D) T cells.
Step-by-step explanation:
The type of white blood cell that plays a key role in adaptive immunity by seeking out, attacking, and destroying targeted pathogens is the T cell (T lymphocyte). Unlike B cells, which are responsible for the production of antibodies as part of the humoral immune response, T cells are central to the cell-mediated immune response.
The three types of T cells include cytotoxic T cells, which destroy virus-infected cells; helper T cells, which activate the immune response; and suppressor T cells, which modulate the immune response to prevent it from becoming too intense. Therefore, the correct answer to the question is D) T cells.