## Core Concept
The question tests understanding of genetics related to apoptosis, which is programmed cell death. Apoptosis plays a crucial role in development, homeostasis, and eliminating damaged cells. The balance between pro-apoptotic and anti-apoptotic genes determines the fate of a cell.

## Why the Correct Answer is Right
The correct answer, **Bcl-2 (B)**, is an anti-apoptotic gene. Bcl-2 (B-cell lymphoma 2) is a key regulator of apoptosis. It works by inhibiting the release of cytochrome c from mitochondria, which is a critical step in the intrinsic pathway of apoptosis. By preventing this release, Bcl-2 effectively acts as a brake on the apoptotic process, promoting cell survival.

## Why Each Wrong Option is Incorrect
- **Option A:** *p53* is actually a tumor suppressor gene that can induce apoptosis in response to DNA damage. It is not anti-apoptotic but rather pro-apoptotic under certain conditions.
- **Option C:** *Bax* (Bcl-2-associated X protein) is a pro-apoptotic gene. It works against Bcl-2 by promoting the release of cytochrome c from mitochondria, thereby facilitating apoptosis.
- **Option D:** *Fas* (CD95) is a receptor that, upon binding to its ligand, can induce apoptosis through the extrinsic pathway. It is involved in the regulation of immune responses and is not anti-apoptotic.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the balance between pro- and anti-apoptotic genes is crucial in cancer development. Overexpression of anti-apoptotic genes like **Bcl-2** can contribute to oncogenesis by allowing damaged cells to survive, while loss of function in pro-apoptotic genes can also lead to cancer.

## Correct Answer: B. Bcl-2.