**Core Concept**
B cell functions involve the activation, proliferation, and differentiation of B lymphocytes into antibody-secreting plasma cells or memory B cells. B cells play a crucial role in the adaptive immune response, particularly in the humoral immunity.

**Why the Correct Answer is Right**
The correct answer is related to the assessment of B cell functions. B cells can be tested through various methods, including:

* **Option B:** Proliferation assays, which measure the ability of B cells to divide and proliferate in response to antigens or mitogens.
* **Option C:** Immunoglobulin production, which evaluates the ability of B cells to produce antibodies in response to antigens.

**Why Each Wrong Option is Incorrect**
* **Option A:** Not applicable - the question is incomplete and cannot be evaluated.
* **Option D:** Not a valid method for testing B cell functions - the correct answer should be a method that is not typically used to assess B cell functions.

**Clinical Pearl / High-Yield Fact**
B cells can be activated through two main pathways: the T cell-dependent pathway, which requires the help of T helper cells, and the T cell-independent pathway, which does not require T cell help.

**Correct Answer:** Not Applicable.