**Core Concept**
Memory cells, such as plasma cells and B memory cells, play a crucial role in long-term immune memory. They are resistant to apoptosis, a process of programmed cell death, which allows them to persist and respond to future infections.

**Why the Correct Answer is Right**
The presence of B cell-activating factor (BAFF) is responsible for the resistance of memory cells to apoptosis. BAFF binds to its receptors, such as BAFFR and BCMA, on the surface of memory cells, promoting their survival and proliferation. This is essential for maintaining long-term immune memory and preventing the depletion of memory cells.

**Why Each Wrong Option is Incorrect**
**Option A:** Although B cell-activating factor (BAFF) is not the correct answer, it is related to the concept. However, the question asks for a growth factor that prevents apoptosis in memory cells, and BAFF is not the primary factor involved.

**Option B:** No growth factor is mentioned here. This option is incomplete and does not address the question.

**Option C:** No growth factor is mentioned here. This option is incomplete and does not address the question.

**Option D:** No growth factor is mentioned here. This option is incomplete and does not address the question.

**Clinical Pearl / High-Yield Fact**
BAFF is a crucial growth factor for B cell survival and differentiation. Its dysregulation has been implicated in autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus.

**Correct Answer:** B. BAFF (B cell-activating factor)