**Core Concept:** Ovulation is the rupture of the follicle containing the mature egg in the ovaries, resulting in the release of the egg for fertilization. Signs of ovulation include:

1. Ovulation may be detected through hormonal changes in the body, such as an increase in LH (Luteinizing Hormone) levels, especially when accompanied by a surge in FSH (Follicle-Stimulating Hormone) levels.
2. Other signs of ovulation include the release of an inflammatory substance called prostaglandin, which causes the cervix to soften and the uterine lining to thicken, preparing for potential implantation.

**Why the Correct Answer is Right:** The correct answer, D, refers to the surge in LH levels which is a key sign of ovulation. The LH surge is a result of the hypothalamus releasing GnRH (Gonadotropin-Releasing Hormone), which triggers the pituitary gland to release LH and FSH. This surge leads to the rupture of the follicle containing the mature egg, releasing the egg for fertilization.

**Why Each Wrong Option Is Incorrect:**

A. Hormonal changes: Other options mention hormonal changes, but only option D specifically refers to the LH surge, which is the key sign of ovulation.
B. Prostaglandin release: While prostaglandin is involved in cervical softening and uterine thickening, option C focuses on prostaglandin, not ovulation.
C. Increase in FSH levels: The correct answer should specifically mention LH surge, not FSH increase, which is responsible for the cascade of hormonal changes leading to ovulation.

**Clinical Pearl:** The clinical pearl here is that understanding the hormonal changes leading to ovulation is crucial in assessing fertility and managing reproductive health issues.