The primary causes of duodenal ulcers include:

Choice A reason: H. pylori infection is a well-known cause of duodenal ulcers. This bacterium damages the protective lining of the stomach and duodenum, leading to inflammation and ulceration. It is one of the most common causes of peptic ulcers worldwide.
Choice D reason: Nonsteroidal anti-inflammatory drugs (NSAIDs) are another primary cause of duodenal ulcers. These medications can irritate the stomach lining and increase acid production, leading to ulcer formation. Long-term use of NSAIDs is particularly associated with this risk.
E reason: Chronic alcohol (ETOH) abuse can also lead to duodenal ulcers. Alcohol irritates the stomach lining and increases acid production, which can contribute to the development of ulcers. Additionally, alcohol abuse can impair the healing process of existing ulcers.
Choice B reason: Side effects of antibiotics are not typically associated with the primary causes of duodenal ulcers. While antibiotics can cause gastrointestinal disturbances, they are not a common cause of ulcer formation.
Choice C reason: Trauma is not a primary cause of duodenal ulcers. While severe physical stress or injury can lead to stress ulcers, these are different from the typical duodenal ulcers caused by H. pylori infection, NSAIDs, or chronic alcohol abuse.

Choice A reason:
Pulmonary embolism is not a typical complication of a peptic ulcer. While serious, pulmonary embolism is unrelated to the gastrointestinal tract and would not arise from ulceration of the stomach or duodenum. It is therefore not the correct answer to the question posed.
Choice B reason:
Bleeding is the primary clinical manifestation of greatest concern with a peptic ulcer. Ulcers can erode into blood vessels, leading to gastrointestinal hemorrhage, which may present as hematemesis (vomiting blood) or melena (black, tarry stools). Severe bleeding can result in hypovolemic shock and requires immediate medical intervention, such as endoscopic hemostasis, blood transfusions, or surgery. This makes bleeding the most critical concern among the options listed.
Choice C reason:
Bowel obstruction can occur as a complication of peptic ulcer disease but is less common compared to bleeding. It arises from scarring or swelling near the pylorus, leading to gastric outlet obstruction. While serious, it is not the most frequent or immediate concern in the context of peptic ulcers.
Choice D reason:
Hepatomegaly, or enlargement of the liver, is unrelated to peptic ulcer disease. This symptom is typically associated with liver conditions such as cirrhosis, hepatitis, or cancer, and does not result from ulcer pathology.