The correct answer is Option B: Progesterone. Here's why: After ovulation, the corpus luteum releases progesterone. Progesterone prepares the endometrium (the lining of the uterus) by thickening it, making it suitable for the implantation of a fertilized egg. Although estradiol (Option A) plays a key role in the initial growth of the uterine lining, it is progesterone that ensures the lining is receptive. Testosterone (Option C) and thyroxin (Option D) do not have a direct role in preparing the uterus for implantation. Thus, progesterone is essential for a successful implantation process.
