Which of the following diseases is caused by the deficiency of Vitamin A?

The correct answer is A, Night blindness. Vitamin A, chemically retinol, is needed to make rhodopsin, the light-sensitive pigment in the rod cells of the retina that lets us see in dim light. When the vitamin is short, the eye cannot adjust to darkness, and the person cannot see properly at night or in poor light; this is night blindness (nyctalopia). If the deficiency continues, the eye becomes dry and the cornea is damaged, a condition called xerophthalmia, which can end in total blindness. Vitamin A is fat-soluble and comes from carrots, papaya, mango, green leafy vegetables, milk, eggs and fish liver oil. B is wrong because scurvy, with bleeding gums, is caused by lack of vitamin C. C is wrong because marasmus is caused by a severe shortage of both calories and protein in young children. D is wrong because kwashiorkor is a protein deficiency disease marked by a swollen belly. Exam tip: vitamin A night blindness, C scurvy, D rickets, K bleeding; marasmus and kwashiorkor are protein-energy problems, not vitamin diseases.