**Core Concept**
The question tests the student's knowledge of antiapoptotic genes, which are crucial in preventing programmed cell death. In the context of cancer and cellular biology, understanding the role of these genes is vital for grasping the mechanisms of tumorigenesis and resistance to chemotherapy.

**Why the Correct Answer is Right**
Bcl-2 (B-cell lymphoma 2) is a key antiapoptotic gene that inhibits apoptosis by interacting with proapoptotic proteins such as Bax and Bak. It does so by preventing the release of cytochrome c from the mitochondria, thus blocking the activation of caspases and subsequent cell death. Bcl-2 is often overexpressed in various types of cancer, contributing to tumor progression and resistance to therapy.

**Why Each Wrong Option is Incorrect**
**Option A:**
- Bcl-xL is an antiapoptotic protein, but the question specifically asks for a gene, and Bcl-xL is a protein product of the BCL2L1 gene.

**Option C:**
- Bax is a proapoptotic gene that promotes cell death, making it an incorrect choice for an antiapoptotic gene.

**Option D:**
- Caspase-3 is a key executioner caspase involved in the apoptosis pathway, but it is not an antiapoptotic gene.

**Clinical Pearl / High-Yield Fact**
It is essential for clinicians to understand the role of Bcl-2 in cancer, as its overexpression can contribute to chemotherapy resistance. Inhibitors of Bcl-2, such as ABT-199, are being explored as potential cancer therapies.

**Correct Answer:** C. Bax is a proapoptotic gene that promotes cell death, making it an incorrect choice for an antiapoptotic gene.