**Core Concept**
Ovulation is a critical phase in the menstrual cycle where a mature ovum is released from the ovarian follicle into the fallopian tube, making it available for fertilization. This process is regulated by a complex interplay of hormones, including estrogen and progesterone.

**Why the Correct Answer is Right**
The sudden rise in luteinizing hormone (LH) is the key event associated with ovulation. LH surge, triggered by a decrease in estrogen levels, causes the rupture of the dominant follicle, releasing the ovum into the fallopian tube. This LH surge is essential for ovulation, as it triggers the final stages of follicular maturation and ovum release. The LH surge is mediated by the hypothalamic-pituitary-gonadal axis, which regulates the menstrual cycle.

**Why Each Wrong Option is Incorrect**
**Option A:** While estrogen levels do increase during the follicular phase, the sudden rise in estrogen is not directly associated with ovulation.
**Option B:** Progesterone levels increase after ovulation, but the sudden rise in progesterone is not the primary trigger for ovulation.
**Option C:** FSH (Follicle-Stimulating Hormone) is essential for follicular growth, but the sudden rise in FSH is not directly associated with ovulation.

**Clinical Pearl / High-Yield Fact**
A key clinical application of understanding ovulation is in the management of infertility. Identifying the timing of ovulation can help couples optimize their chances of conception through timing intercourse or assisted reproductive technologies.

**Correct Answer: D. Luteinizing hormone (LH) surge.**