**Core Concept**
The separation of the first polar body is a critical event in oogenesis, marking the beginning of meiosis in the oocyte. This process involves the release of the first polar body from the oocyte, which is essential for the formation of the secondary oocyte.

**Why the Correct Answer is Right**
The separation of the first polar body occurs simultaneously with the completion of the first meiotic division, specifically during the anaphase I stage. This event is mediated by the spindle fibers, which separate the homologous chromosomes and release the first polar body. The first polar body contains half of the chromosomes, while the secondary oocyte retains the other half. This process is crucial for the proper segregation of genetic material during meiosis.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the separation of the first polar body does not occur during metaphase I, when the homologous chromosomes are aligned at the metaphase plate.
* **Option B:** This option is incorrect because the separation of the first polar body does not occur during telophase I, when the nuclear envelope begins to reform around the chromosomes.
* **Option C:** This option is incorrect because the separation of the first polar body does not occur during anaphase II, when the sister chromatids are separated.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the separation of the first polar body marks the beginning of meiosis in the oocyte, and any disruption in this process can lead to errors in genetic material segregation, resulting in abnormalities such as aneuploidy.

**Correct Answer: C. Anaphase I.**