## Core Concept
Radiotherapy is a treatment modality that uses ionizing radiation to kill or control malignant cells. It is commonly used in the management of various types of cancers. The effectiveness of radiotherapy depends on the type and stage of cancer, as well as the overall health of the patient.

## Why the Correct Answer is Right
The correct answer, **C. Early stage Hodgkin's lymphoma**, is a condition where radiotherapy is indeed considered a treatment of choice, especially in early stages. Radiotherapy works by damaging the DNA of cancer cells, thereby inhibiting their ability to grow and divide. In the case of Hodgkin's lymphoma, radiotherapy has been shown to be highly effective in achieving long-term remission and even cure, particularly when used in combination with chemotherapy.

## Why Each Wrong Option is Incorrect
* **Option A:** This option is not provided, but typically, other cancers or conditions might be listed here. Generally, radiotherapy is not the sole treatment of choice for many advanced cancers or those with widespread metastasis.
* **Option B:** Similarly, without the specific option, it's hard to address directly, but usually, other conditions might require a combination of surgery, chemotherapy, and radiotherapy.
* **Option D:** This option is also not provided, but commonly, conditions that are more effectively treated with surgery or chemotherapy might be listed here.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **Hodgkin's lymphoma** is highly radiosensitive, meaning it responds well to radiation therapy. This makes radiotherapy a cornerstone in the treatment of early-stage Hodgkin's lymphoma, often leading to high cure rates.

## Correct Answer: C. Early stage Hodgkin's lymphoma