## Core Concept
Grave's thyrotoxicosis, also known as Graves' disease, is an autoimmune disorder that leads to hyperthyroidism. The definitive treatment aims to reduce thyroid hormone production or its effects. Treatment options include antithyroid medications, radioactive iodine ablation, and surgery.

## Why the Correct Answer is Right
The correct answer, radioactive iodine ablation (option not explicitly listed but implied as the best choice), works by destroying part or all of the thyroid gland, thereby reducing thyroid hormone production. This method is considered definitive because it directly addresses the overproduction of thyroid hormones by reducing the gland's mass. It is a preferred long-term solution for many patients with Graves' disease.

## Why Each Wrong Option is Incorrect
- **Option A:** Antithyroid medications (e.g., methimazole, propylthiouracil) are used to manage hyperthyroidism symptoms by inhibiting thyroid hormone synthesis but are not considered definitive treatments as they do not destroy thyroid tissue and often require long-term use.
- **Option B:** Beta blockers may help manage symptoms such as tachycardia and tremors but do not affect thyroid hormone production or the underlying cause of Graves' disease.
- **Option C:** Surgical removal of part or all of the thyroid gland (thyroidectomy) is a definitive treatment but is usually reserved for specific cases due to associated risks.

## Clinical Pearl / High-Yield Fact
A key point to remember is that radioactive iodine ablation is often the preferred definitive treatment for Graves' disease in many patients, especially those who have relapsed after antithyroid medication or have a large goiter. However, it may not be suitable for everyone, such as pregnant women.

## Correct Answer Line
**Correct Answer: D. Radioactive iodine ablation.**