Primary lymphoid organs: These organs include the bone marrow and the thymus. They create special immune system cells called lymphocytes. Secondary lymphoid organs: These organs include the lymph nodes, the spleen, the tonsils and certain tissue in various mucous membrane layers in the body (for instance in the bowel).
Answer:
All of the above
Explanation:
I took the test and got an A
Press two fingers over a vein and count the beats for thirty seconds and double it or for a full minute