Which of the following is TRUE regarding lymph nodes?

A) They are located only in the digestive tract and neck.
B) They remove microorganisms and abnormal cells from the lymph and return them to blood circulation.
C) Macrophages but not lymphocytes can be found within lymph nodes.
D) They filter lymph fluid, trapping microorganisms and abnormal cells.
E) Lymph flows from the lymph vessels to the urinary system.