**Core Concept**
Apoptosis, also known as programmed cell death, is a crucial process in maintaining tissue homeostasis and eliminating damaged or unwanted cells. Pro-apoptotic factors are molecules that promote apoptosis by activating the caspase cascade, leading to cell death.

**Why the Correct Answer is Right**
The correct answer is a pro-apoptotic factor because it binds to and inhibits the anti-apoptotic protein Bcl-2, thereby releasing the pro-apoptotic protein Bax from the mitochondrial membrane. This allows Bax to oligomerize and form pores in the mitochondrial outer membrane, releasing cytochrome c into the cytosol. Cytochrome c then binds to Apaf-1, leading to the activation of caspase-9 and the subsequent activation of caspase-3, resulting in cell death.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it is an anti-apoptotic factor, which would inhibit apoptosis rather than promote it.
* **Option B:** This option is incorrect because it is a survival factor that promotes cell survival and proliferation, rather than inducing cell death.
* **Option C:** This option is incorrect because it is involved in cell proliferation and survival, and its dysregulation can lead to cancer, rather than promoting apoptosis.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the balance between pro-apoptotic and anti-apoptotic factors is crucial in determining cell fate. Dysregulation of this balance can lead to various diseases, including cancer and neurodegenerative disorders.

**Correct Answer: B. Bim (BCL2L11)**