Arrange the following events of the menstrual cycle in correct sequence.
a) release of an egg from the ovary
b) breakdown of the thickened inner wall of the uterus
c) thickening of the wall of the uterus
d) maturation of the ovum
d → a → c → b
Every month, usually one egg matures and is released from an ovary by a process called ovulation. In the meantime, the inner lining of the uterus starts thickening and continues to do so even after ovulation, in order to prepare for a fertilised egg. If fertilisation does not happen, the thickened inner lining is broken down and shed in the form of blood.