The correct option is B. For a mature woman, each month the increased level of estrogen hormone leads the pituitary gland to secrete luteinizing hormone. Once this hormone is secreted, the ovary releases a single egg which moves down to the lining of the uterus. If fertilization does not occur, the egg is shed together with the lining of the uterus in a monthly process called mensuration. If fertilization occur, then the fertilized egg attach to the lining of the uterus and placenta is formed. The fertilized egg then send signal to the ovary to keep secreting progesterone, which will sustaining the pregnancy by keeping the uterus lining thick and nourishing for the developing embryo.
