Final answer:
Carbohydrate malabsorption leads to osmotic diarrhea with low pH due to the retention of water in the intestines by undigested carbohydrates, making answer (a) correct.
Step-by-step explanation:
Carbohydrate malabsorption causes osmotic diarrhea with low pH, making answer (a) the correct choice. Osmotic diarrhea occurs when undigested carbohydrates in the small intestine and colon attract and retain water, increasing stool output and fluidity. This is contrasted with secretory diarrhea, where there is an active secretion of electrolytes and water into the bowel; inflammatory diarrhea, which involves damage to the mucosal lining; and motility-related diarrhea, which is due to the rapid movement of food through the intestines. Carbohydrate malabsorption, as seen in conditions such as lactase deficiency, leads to the fermentation of undigested carbohydrates by bacteria, producing gas, and resulting in an acidic environment in the gut, thereby causing osmotic diarrhea with a low pH.