Mother’s milk provides almost complete diet to the new-born, but it lacks the following

Breast milk is the ideal first food for a newborn, but it is low in iron, along with vitamin D, vitamin K and fluoride. That is why the question asks for the missing nutrient, and the answer is A.

The iron content of breast milk is small, but its bioavailability is high, so a healthy term baby absorbs it well. The infant also draws on iron stores built up in the womb, which last roughly until six months. After that, iron-rich complementary food becomes essential, and this is the Mains link to child anaemia, NFHS data and Anemia Mukt Bharat.

• B (Calcium): Human milk has less calcium than cow's milk, but the amount is adequate and absorbed efficiently, so it is not a missing nutrient.
• C (Magnesium): Present in sufficient amounts in breast milk.
• D (Potassium): Present in sufficient amounts in breast milk.

Trap: Students confuse "lower in quantity" with "absent" and pick calcium because cow's milk is rich in it. The question asks what breast milk lacks, not what it has less of.