As for this question, the answer would be B. kidney.
GU system or what they call as the Genitourinary system and may also be referred to as urogenital system is the system of both the reproductive system and the urinary system. They can be classified together into one system due to their immediate proximity, their origin during the embryological stages, and also the usage of a common organ. Rectum would be part of the excretory system. Lymph nodes would be of the lymphatic system and the adrenal gland would be in the endocrine system.
