Select the correct option regarding the function of gonadotropins in a pregnant woman.

• A
  High levels of $FSH$ and $LH$ stimulate the development of the endometrium.
• B
  High levels of $FSH$ and $LH$ facilitate implantation.
• C
  High levels of $HCG$ stimulate the synthesis of estrogen and progesterone.
• D
  High levels of $HCG$ stimulate the development of the endometrium.