**Core Concept**
Classical Hodgkin's lymphoma (HL) is a type of lymphoma characterized by the presence of distinctive neoplastic cells called Reed-Sternberg cells, which are accompanied by a reactive background of non-neoplastic cells.

**Why the Correct Answer is Right**
The correct answer highlights the key histological feature of classical Hodgkin's disease, which is the presence of Reed-Sternberg cells. These cells are large, multinucleated cells with a distinct appearance, and they are a hallmark of classical HL. The reactive background of non-neoplastic cells, including lymphocytes, histiocytes, and plasma cells, is also a characteristic feature of this disease. The presence of Reed-Sternberg cells is essential for the diagnosis of classical HL.

**Why Each Wrong Option is Incorrect**
**Option A:** Mixed cellularity is seen in the background of some types of lymphomas, but it is not a specific feature of classical Hodgkin's disease. Mixed cellularity lymphoma is a different subtype of lymphoma altogether.
**Option B:** In classical HL, the number of non-neoplastic cells is often greater than the number of neoplastic cells, which is the opposite of what this option states.
**Option C:** While both neoplastic and non-neoplastic cells are indeed seen in classical HL, this option is too vague and does not specifically highlight the distinctive features of this disease.
**Option D:** CD15 and CD34 are markers that can be expressed by Reed-Sternberg cells, but this option does not directly address the histological features of classical HL.

**Clinical Pearl / High-Yield Fact**
When diagnosing lymphomas, it's essential to look for distinctive neoplastic cells, such as Reed-Sternberg cells, which are a hallmark of classical Hodgkin's lymphoma. Remember the acronym "RS" to remind you of Reed-Sternberg cells.

**Correct Answer:** E. Reed sternberg cells are seen