**Core Concept**
Folliculogenesis is the complex process of follicular development and maturation in the ovaries, culminating in ovulation. It involves a coordinated interplay of hormones, growth factors, and cellular interactions. Understanding the underlying mechanisms of folliculogenesis is crucial for comprehending ovulatory processes.

**Why the Correct Answer is Right**
Option D is incorrect because elevated and static levels of estradiol are not essential for ovulation. Instead, a surge in estradiol levels, coupled with a decrease in progesterone levels, triggers the preovulatory LH surge, which in turn induces ovulation. This precise balance of hormones is critical for successful ovulation.

**Why Each Wrong Option is Incorrect**
**Option A:** Follicular development and differentiation indeed take about 85 days, but this statement is not relevant to the question's focus on the mechanisms of ovulation. The duration of follicular development is a separate aspect of folliculogenesis.
**Option B:** Anti-Müllerian hormone (AMH) is actually involved in suppressing follicular development and oocyte maturation. High levels of AMH can inhibit follicular growth, making option B incorrect.
**Option C:** The first phase of follicular growth is indeed gonadotrophin-insensitive, as it is primarily driven by the local growth factors and hormones within the ovary. This phase is characterized by the growth of primordial follicles into primary follicles.

**Clinical Pearl / High-Yield Fact**
A key concept in folliculogenesis is the importance of the LH surge in triggering ovulation. The LH surge is a critical event that marks the transition from the follicular to the luteal phase of the menstrual cycle. Understanding this process is essential for managing fertility and treating ovulatory disorders.

**Correct Answer:**
✓ Correct Answer: D. Elevated and static levels of estradiol is essential for ovulation