Biomolecules

The fat-soluble vitamins are A, D, E and K.
Retinol is vitamin A, a fat-soluble vitamin. Its deficiency causes night blindness and xerophthalmia (dryness of the conjunctiva and cornea). So this pair is correct on both counts.
Cobalamine is vitamin $B_{12}$, which is water soluble; its deficiency causes pernicious anaemia. Beri-beri is caused by the deficiency of thiamine (vitamin $B_1$).
Calciferol is vitamin D, which is fat soluble, but its deficiency causes rickets in children and osteomalacia in adults. Pellagra is caused by the deficiency of niacin (vitamin $B_3$).
Ascorbic acid is vitamin C; it is correctly matched with scurvy, but it is a water-soluble vitamin.
So the fat-soluble vitamin correctly matched with its deficiency disease is Retinol - Xerophthalmia.

Only a few elements make up almost the whole mass of a living organism.
Oxygen (about 65 percent), carbon (about 18.5 percent), hydrogen (about 9.5 percent) and nitrogen (about 3.3 percent) together make up about 96 percent of the body mass.
The next most abundant elements by mass are calcium (about 1.5 percent) and phosphorus (about 1 percent).
Calcium and phosphorus are present in large amounts in bones and teeth; phosphorus is also a part of nucleic acids, ATP and phospholipids.
These six elements together account for about 98 to 99 percent of the mass.
Sulphur, sodium and magnesium are each present in amounts of less than about 0.3 percent.
So, going by mass, the two remaining elements are calcium and phosphorus, as given in the answer key.