**Core Concept**
A Schatzki ring is a narrow ring of tissue that can cause esophageal obstruction. It is a type of mucosal web located at the junction of the esophagus and the stomach, specifically at the lower end of the esophagus. This anatomical structure is a common cause of dysphagia in adults.

**Why the Correct Answer is Right**
The Schatzki ring is located at the junction of the esophagus and the stomach, where the esophageal mucosa transitions into the gastric mucosa. This is the area where the lower esophageal sphincter (LES) is located, and it is a common site for the formation of mucosal webs and rings. The Schatzki ring is thought to be a congenital anomaly, and it can cause symptoms such as dysphagia, especially with solid foods. The lower end of the esophagus is the correct location of the Schatzki ring due to its proximity to the LES and the transition zone between the esophagus and the stomach.

**Why Each Wrong Option is Incorrect**
**Option A:** The lower end of the pharynx is not the correct location of the Schatzki ring, as the pharynx is a separate anatomical structure that connects the oral cavity to the esophagus.

**Option B:** The upper end of the esophagus is not the correct location of the Schatzki ring, as this area is primarily responsible for the passage of food from the pharynx to the esophagus.

**Option D:** The antrum of the stomach is not the correct location of the Schatzki ring, as the antrum is a region of the stomach that is responsible for the storage and mixing of food, and it is not directly adjacent to the lower end of the esophagus.

**Clinical Pearl / High-Yield Fact**
The Schatzki ring is a common cause of dysphagia in adults, especially in individuals over the age of 50. It is often associated with symptoms of esophageal obstruction, such as difficulty swallowing solid foods and regurgitation of food.

**✓ Correct Answer: C. Lower end of esophagus**