**Core Concept**
The process of oocyte maturation and ovulation involves the release of the first polar body, which is a crucial step in the formation of a mature oocyte. This event occurs due to the meiotic division of the oocyte, where the oocyte undergoes two successive cell divisions without an intervening S phase.

**Why the Correct Answer is Right**
The first polar body is extruded at the completion of the first meiotic division (meiosis I), resulting in the formation of a secondary oocyte and a first polar body. This event is mediated by the activation of the meiosis-activating sterol (MAS) and the subsequent breakdown of the germinal vesicle. The first polar body contains one set of chromosomes, whereas the secondary oocyte contains the remaining set of chromosomes that will be divided during the second meiotic division (meiosis II).

**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect because the first polar body is not extruded during the process of fertilization, which occurs after the completion of meiosis II.
* **Option B:** This is incorrect because the first polar body is not extruded during the process of follicular development, which occurs before ovulation.
* **Option C:** This is incorrect because the first polar body is not extruded during the process of luteinization, which occurs after ovulation.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the first polar body is extruded at the completion of meiosis I, resulting in the formation of a secondary oocyte and a first polar body. This event is a critical step in the formation of a mature oocyte and is essential for ovulation.

**Correct Answer: B. During the first meiotic division.**