**Core Concept**
The question is testing the understanding of the pathophysiology of anemia in the context of gastric resection. **Anemia** is a condition characterized by a decrease in the number of red blood cells or the amount of hemoglobin in the blood, leading to inadequate oxygen delivery to tissues. In the context of gastric resection, the body's ability to absorb iron, a crucial component of hemoglobin, is affected.

**Why the Correct Answer is Right**
The correct answer is related to the type of gastric resection that affects the absorption of iron. Gastric resection, particularly **proximal gastrectomy**, can lead to anemia due to impaired iron absorption. The stomach's parietal cells, which produce gastric acid, are also responsible for the secretion of **intrinsic factor**, a protein essential for the absorption of vitamin B12. However, the question is focused on anemia related to iron deficiency.

**Intrinsic factor** is crucial for the absorption of dietary iron in the ileum. When the stomach is removed or significantly reduced in size, the production of intrinsic factor decreases, leading to impaired iron absorption and subsequent anemia. This is particularly relevant in the context of **proximal gastrectomy**, where a significant portion of the stomach, including the parietal cells, is removed.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the context of gastric resection and anemia. **Pyloric gastrectomy** involves the removal of the pylorus, which is not directly related to iron absorption.
* **Option B:** While **distal gastrectomy** involves the removal of the distal part of the stomach, it is less likely to affect iron absorption compared to proximal gastrectomy.
* **Option C:** This option is not relevant to the context of gastric resection and anemia. **Gastrojejunostomy** is a surgical procedure that involves the creation of a connection between the stomach and the jejunum, which is not directly related to iron absorption.

**Clinical Pearl / High-Yield Fact**
In patients with gastric resection, particularly proximal gastrectomy, it is essential to monitor iron levels and consider iron supplementation to prevent anemia. Additionally, patients with gastric resection are at increased risk of developing vitamin B12 deficiency due to impaired intrinsic factor production.

**Correct Answer: C. Distal gastrectomy.**