Which of the following nutrients are present in milk?

Concept: Milk's nutrient identity, as taught in general science and EVS pedagogy, rests on a characteristic triad — a high-quality protein, the mineral calcium, and vitamin D (the fat-soluble vitamin that aids calcium absorption) — the standard set through which milk's nutritional value is described in textbooks.

Application: Whole milk is one of the most recognized dietary sources of both protein and calcium; it also carries small natural amounts of vitamin D that are commonly boosted through fortification. The CTET official key treats protein, calcium, and vitamin D together as milk's defining nutrient set. Among the four combinations offered, only 'Protein, Calcium, Vitamin D' matches this recognized profile.

Cross-check: Checking each of the other combinations against milk's actual composition confirms the choice, since none of them matches:

• Protein, Vitamin C, Vitamin A — vitamin C is a nutrient associated with citrus fruits and vegetables, not dairy, so milk is not recognized as a source of it.

• Carbohydrates, Vitamin C, Iron — milk does contain lactose as its carbohydrate, but vitamin C and iron are not characteristic milk nutrients, which is what breaks this combination.

• Protein, Iron, Vitamin D — protein and vitamin D fit, but milk is a poor dietary source of iron, so this combination fails on its middle nutrient.

This matches the official CTET (July 2019, Paper II) answer key, which marks Protein, Calcium, Vitamin D as the correct combination.