Which structure of the female reproductive system is the source of the blood and mucosal tissue during menstruation?

The correct answer is B: Endometrium. The endometrium is the inner lining of the uterus where an embryo implants during pregnancy. If no pregnancy occurs, the endometrial lining sheds during menstruation, leading to the discharge of blood and mucosal tissue. The fallopian tubes are responsible for transporting the egg from the ovary to the uterus. The cervix is the lower part of the uterus that connects to the vagina. The ovaries produce eggs and hormones, but they are not the source of blood and mucosal tissue during menstruation.