Constituents of food which enhance calcium absorption are:

• A. Vitamins C & D
• B. Vitamins A & K
• C. Vitamins E & B
• D. Vitamins D & K

Answer: (A)

Calcium absorption in the gut is boosted mainly by vitamin D, which increases the intestinal machinery that transports calcium into the bloodstream. This makes vitamin D the key nutrient that enhances calcium uptake from the diet. The pairing that includes vitamin D with vitamin C fits with this idea: vitamin D provides the strong boost to absorption, and vitamin C can support mineral availability in the gut, for example by helping form more soluble calcium salts in some contexts, which can facilitate uptake. The other vitamins listed don’t have a direct, well-established effect on intestinal calcium transport, since vitamins A and K are more tied to bone metabolism than absorption, and vitamins E and B don’t notably enhance calcium uptake. Thus, the combination of vitamin D with vitamin C best aligns with the mechanism of improving calcium absorption.