Absorption of iron:

Correct Answer: D

Rationale: The correct answer is D because iron absorption is regulated to meet the body's needs. When body stores are low or erythropoiesis is increased, absorption increases. This process occurs mainly in the duodenum and upper jejunum, not the terminal ileum as stated in option C. Option A is incorrect because HCl aids in converting iron into a more absorbable form but does not determine the percentage absorbed. Option B is incorrect as the majority of iron absorption occurs in the duodenum and upper jejunum, not the small intestine in general.

Correct Answer: B

Rationale: B: Carcinoma of the esophagus is difficult to cure due to local spread. Esophageal cancer often presents at advanced stages, making complete surgical resection challenging. Local spread to nearby structures like the trachea or blood vessels hinders curative treatment. This is supported by the fact that esophageal cancer has a poor prognosis, with a 5-year survival rate of around 20%. A: This is incorrect because esophageal carcinoma is often diagnosed at advanced stages when symptoms appear, making it less curable than early-stage cancers. C: Early widespread metastases are not a defining feature of esophageal carcinoma. Metastases typically occur at later stages of the disease. D: Esophageal carcinoma can be differentiated or undifferentiated, but this does not impact the difficulty in curing the cancer due to local spread.

Correct Answer: B

Rationale: The correct answer is B: Metabolic alkalosis. Vomiting causes loss of stomach acid (HCl), leading to an increase in blood pH and bicarbonate levels, resulting in metabolic alkalosis. Choice A is incorrect because vomiting does not lead to an increase in acid levels. Choices C and D are incorrect as they are related to respiratory disorders, not directly caused by vomiting. In summary, vomiting leads to metabolic alkalosis due to loss of stomach acid.

Correct Answer: A

Rationale: Rationale: Loperamide is an opioid receptor agonist that acts on the gut to slow down intestinal motility. This results in the slowed transit of intestinal contents, similar to how morphine works. This helps in alleviating diarrhea. Therefore, the correct answer is A. Choices B and C are incorrect because loperamide and morphine do not cause more rapid gastric emptying or increased colonic secretion of chloride ion. Choice D is incorrect as the correct answer has been explained.

Correct Answer: C

Rationale: The correct answer is C: Water absorption and feces formation. The primary function of the large intestine is to absorb water from the undigested food material and form feces. This process helps in maintaining the body's water balance and producing solid waste for excretion. The large intestine does not primarily absorb nutrients like the small intestine (Choice A), nor does it digest proteins (Choice D). Choice B is irrelevant and does not describe the main function of the large intestine in digestion.