4. All of the following types are white blood cells, except a. Platelets b. Tcells c. Neutrophils d. Lymphocytes

The correct answer is a. Platelets.<br /><br />Platelets, also known as thrombocytes, are not white blood cells. They are small, irregularly shaped cell fragments that play a crucial role in blood clotting and wound healing. Platelets are produced in the bone marrow and circulate in the bloodstream. They are different from white blood cells, which are part of the immune system and help fight infections and other diseases.