Q.Which of the following is a water-soluble vitamin? a. Vitamin A b. Vitamin B c. Vitamin D d. Vitamin K

The textbook's two vitamin tables (2.i and 2.ii) are built around one key distinction: how the body handles the excess.

Water-soluble vitamins — all the B-vitamins (B1 Thiamine, B2 Riboflavin, B3 Niacin, B6, Biotin, Pantothenic acid, Folic acid/B9, B12 Cobalamin) and vitamin C — dissolve in water. Whatever the body doesn't use passes out through the kidneys as urine, so the body needs frequent small doses and these vitamins are unlikely to reach toxic levels even at higher intakes.

Fat-soluble vitamins — A, D, E and K — dissolve in fat instead. They get stored in the body's cells rather than being excreted, which means a balanced diet usually provides enough of them, but it also means taking large doses (e.g., through unsupervised supplements) can build up to toxic levels over time, unlike water-soluble vitamins. …