Ovulation does not occur during pregnancy in the human female because

• A
  The follicles are not influenced by the level of progesterone in the blood
• B
  The corpus luteum and later the placenta produce large amounts of progesterone
• C
  The corpus luteum degenerates as luteinising hormone is no longer produced
• D
  The embryo produces hormones which retard the production of maternal follicle stimulating hormones