**Core Concept**
A carotid body tumor, also known as a carotid body paraganglioma, is a rare, usually benign neoplasm arising from the carotid body, a chemoreceptor organ located at the bifurcation of the common carotid artery. The primary goal of treatment is complete surgical excision to prevent potential complications such as compression of adjacent structures, malignant transformation, and local recurrence.

**Why the Correct Answer is Right**
The best treatment for a carotid body tumor is surgical excision. This approach allows for the removal of the tumor with minimal risk of complications and recurrence. The surgery is typically performed by a skilled neurosurgeon or otolaryngologist, and may involve a transcervical approach or a more extensive procedure depending on the tumor's size and location. The key to successful surgery is complete removal of the tumor with preservation of the surrounding carotid arteries and cranial nerves.

**Why Each Wrong Option is Incorrect**

**Option B:** Radiotherapy is not the primary treatment for carotid body tumors, as these tumors are typically benign and radiation therapy may lead to radiation-induced damage to surrounding tissues and structures.

**Option C:** Chemotherapy is not an effective treatment for carotid body tumors, as these tumors are usually chemoresistant and do not respond well to systemic chemotherapy.

**Option D:** Carotid artery ligation, both proximal and distal to the tumor, is not a recommended treatment for carotid body tumors. This approach would compromise blood flow to the brain and face, leading to significant morbidity.

**Clinical Pearl / High-Yield Fact**
It's essential for surgeons to thoroughly evaluate the tumor's extent and relationship with surrounding structures before surgery to minimize the risk of complications and ensure complete excision of the tumor.

**✓ Correct Answer: A. Excision of tumor**