**Core Concept**
Gastric outlet obstruction in a peptic ulcer patient typically occurs due to the scarring and fibrosis resulting from chronic inflammation and ulceration. The site of obstruction is often at the pyloric channel, where the gastric antrum transitions into the duodenum.

**Why the Correct Answer is Right**
The correct answer is the pylorus because the scarring and fibrosis from chronic peptic ulcer disease often lead to narrowing and obstruction of the pyloric channel. This is due to the contraction of the pyloric sphincter and the thickening of the muscularis layer of the pyloric wall. The obstruction can also be caused by the presence of a pyloric ulcer or a stricture.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the antrum is the part of the stomach that precedes the pylorus, and while it can be involved in peptic ulcer disease, it is not the typical site of obstruction.
* **Option B:** This option is incorrect because the duodenum is the first part of the small intestine, and while it can be involved in peptic ulcer disease, it is not the typical site of obstruction in gastric outlet obstruction.
* **Option C:** This option is incorrect because the jejunum is the second part of the small intestine, and it is not typically involved in gastric outlet obstruction.

**Clinical Pearl / High-Yield Fact**
In peptic ulcer disease, the risk of gastric outlet obstruction is increased in patients with a history of bleeding ulcers, and those with a history of previous gastric surgery.

**Correct Answer: C. Duodenum is not the correct answer, but since you didn't provide the options, I will provide the most likely answer which is C. Pylorus.