In the Luteal Phase of the Uterine Cycle, the Endometrium

In the luteal phase of the uterine cycle, the endometrium breaks down if there is no pregnancy. What happens differently if there is a pregnancy?

A) The placenta develops immediately to support the embryo in the uterine lining, and it takes over secretion of estrogen and progesterone to maintain the pregnancy.
B) Implantation cues the endometrium to secrete the hormone hCG which keeps the corpus luteum actively secreting estrogen and progesterone to maintain the uterine lining for the 6-7 weeks it takes for the placenta to take over.
C) Implantation cues the endometrium to secrete the hormone testosterone which gives the corpus luteum strength to maintain the uterine lining for the 6-7 weeks it takes for the placenta to form.
D) The embryo itself implants in the uterine lining and begins secreting progesterone and estrogen to keep the corpus luteum active in order to maintain the pregnancy.
E) Implantation cues the corpus luteum to degenerate, estrogen and progesterone levels drop, and endometrium is maintained for the duration of the pregnancy.