What occurs during the female's menstrual cycle?

During the females menstrual cycle, the lining of her uterus sheds all the extra tissue that her body created for a fertilized egg. The egg passes through the uterus and does not attach to the wall of the uterus if not fertilized, causing the tissue created for that reason to shed which is what caused all the "Bleeding", which is actually body tissue. 

Aand b would both be correct