**Core Concept**
Hodgkin's disease, also known as Hodgkin lymphoma, is a type of lymphoma characterized by the presence of distinctive cells called Reed-Sternberg cells. The diagnosis of Hodgkin's disease relies heavily on histopathological examination of lymph node biopsies and the presence of specific markers.

**Why the Correct Answer is Right**
The classical markers for Hodgkin's disease include the presence of Reed-Sternberg cells, which are large, multinucleated cells with a distinctive appearance. These cells are typically found in the lymph nodes and are a hallmark of Hodgkin's disease. The presence of Reed-Sternberg cells is a critical diagnostic feature of Hodgkin's disease, and their absence makes the diagnosis of Hodgkin's disease unlikely.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Hodgkin's disease is not typically associated with the presence of lymphoblasts, which are more characteristic of acute lymphoblastic leukemia (ALL).
**Option B:** This option is incorrect because the presence of plasma cells is more characteristic of multiple myeloma, a different type of cancer.
**Option C:** This option is incorrect because the presence of histiocytes is a non-specific finding that can be seen in a variety of conditions, including infections and inflammatory diseases.

**Clinical Pearl / High-Yield Fact**
The presence of Reed-Sternberg cells is a critical diagnostic feature of Hodgkin's disease, and their absence makes the diagnosis of Hodgkin's disease unlikely. It's essential to recognize the distinctive appearance of Reed-Sternberg cells to make an accurate diagnosis.

**Correct Answer: C. Reed-Sternberg cells.**