**Core Concept**
The germinal cell layer surrounding the oocyte before ovulation is part of the ovarian follicle structure and refers to the cumulus mass, which consists of multiple granulosa cells that surround the oocyte. This layer is essential for oocyte nourishment and protection during follicular development.

**Why the Correct Answer is Right**
The **cumulus oophorus** (or cumulus oophorus) is a layer of granulosa cells that surrounds the oocyte in the mature follicle just before ovulation. These cells form a dense, gelatinous mass that provides structural support and metabolic support to the oocyte. The cumulus oophorus is released during ovulation and is crucial for fertilization, as it facilitates sperm interaction and oocyte pickup.

**Why Each Wrong Option is Incorrect**
Option A: The **zona pellucida** is a thick, acellular glycoprotein layer *directly* surrounding the oocyte, not a germinal cell layer. It is involved in species-specific fertilization and early embryonic development, but not composed of germinal cells.
Option B: The **zona reticularis** is a region of the adrenal cortex, not related to ovarian follicles or oocyte structure.
Option D: The **zona glomerulosa** is another adrenal cortex layer responsible for aldosterone production and has no role in oocyte development.

**Clinical Pearl / High-Yield Fact**
Remember: **Cumulus oophorus = granulosa cells** around the oocyte; **Zona pellucida = glycoprotein layer** on the oocyte surface. In assisted reproduction, cumulus cells are vital for oocyte maturation and fertilization success.

✓ Correct Answer: C. Cumulous oophorus