The correct option is C Both A and R are true, but R is not the correct explanation of A
Menstruation, also known as a period, is the regular (monthly) discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina. The first menstruation begins at puberty and is called menarche and is a sign of fertility in women. It marks that the reproductive phase of a woman is active and is capable of concieving.