**Core Concept**
Cells that express immunoglobulins on their surface play a crucial role in the adaptive immune response, particularly in the activation of immune cells and the elimination of pathogens. This phenomenon is mediated by the specific binding of antibodies to antigens, which triggers various cellular responses.

**Why the Correct Answer is Right**
Cells that display immunoglobulins on their surface are known as **plasma cells**. Plasma cells are terminally differentiated B lymphocytes that produce and secrete large amounts of antibodies, which are essentially immunoglobulins. These molecules are essential for recognizing and neutralizing pathogens, thereby protecting the host from infection. The presence of immunoglobulins on the surface of plasma cells serves as a marker of their activation and function.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided, so we'll proceed to the remaining options.
**Option B:** While B lymphocytes are the precursors to plasma cells, they do not typically display immunoglobulins on their surface in the same manner as plasma cells. B cells express immunoglobulins on their surface as B cell receptors, but this is distinct from the surface expression seen in plasma cells.
**Option C:** T lymphocytes, or T cells, are another type of immune cell, but they do not express immunoglobulins on their surface. T cells recognize antigens through their T cell receptors, which are distinct from immunoglobulins.
**Option D:** Macrophages are a type of immune cell involved in phagocytosis and antigen presentation, but they do not express immunoglobulins on their surface.

**Clinical Pearl / High-Yield Fact**
Plasma cells are the primary producers of antibodies, and their surface expression of immunoglobulins is a hallmark of their activation and function. This phenomenon is a key aspect of the adaptive immune response, enabling the host to mount a targeted and effective response to pathogens.

**Correct Answer:** C. Plasma cells.