[IB Biology SL at GHS: Human Reproduction]
21. As a result in the rise of progesterone levels between days 12 and 21, what event of the menstrual cycle occurs?

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A) The uterine lining continues to thicken in preparation for implantation of the fertilized egg.

B) The uterine lining begins its initial repair and thickening.

C) Ovulation occurs.

D) Menstrual flow occurs.

E) Implantation of the egg in the uterine lining occurs.

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