**Core Concept**
Ovulation is a critical phase in the female menstrual cycle, where a mature ovum is released from the ovary into the fallopian tube. This process is regulated by a complex interplay of hormonal changes, primarily driven by the surge of luteinizing hormone (LH) from the anterior pituitary gland.

**Why the Correct Answer is Right**
The LH surge triggers a series of events, including the rupture of the antral follicle, which releases the ovum into the fallopian tube. This process is mediated by the increased expression of LH receptors on the surface of granulosa cells in the follicle. The LH surge also stimulates the production of progesterone by the corpus luteum, which prepares the uterus for potential implantation of a fertilized ovum.

**Why Each Wrong Option is Incorrect**
* **Option A:** Ovulation does not occur due to the withdrawal of estrogen, as this would lead to a decrease in follicle-stimulating hormone (FSH) and ultimately, follicular growth.
* **Option B:** While estrogen levels do increase during the follicular phase, it is the LH surge, not estrogen, that triggers ovulation.
* **Option C:** Progesterone is involved in the luteal phase, preparing the uterus for implantation, but it is not responsible for the initiation of ovulation.

**Clinical Pearl / High-Yield Fact**
The LH surge is a crucial event in ovulation, and its timing can be influenced by various factors, including stress, sleep deprivation, and certain medical conditions. Understanding the hormonal regulation of ovulation is essential for the management of infertility and other reproductive disorders.

**Correct Answer: D. The LH surge triggers ovulation by stimulating the rupture of the antral follicle and the release of the ovum into the fallopian tube.**