Dr. Tasha is examining one of her patients. She recognizes that the patient’s body is not returning fluid to the bloodstream as it should. Dr. Tasha also learns that the patient is getting sick often and is less able to fight infections than a healthy person. Tasha will most likely tell her patient that the problem is with which body system? A. the endocrine system B. the immune system C. the reproductive system D. the cardiovascular system