Assertion (A): AIDS is caused by a retrovirus. Reason (R): HIV contains RNA and the enzyme reverse transcriptase. MCQ with Answer and Explanation

Explanation:
Kwashiorkor is a severe form of malnutrition caused by inadequate protein intake despite sufficient calorie consumption. Marasmus results from a severe deficiency of both calories and protein, leading to extreme wasting. Goiter is the enlargement of the thyroid gland caused by iodine deficiency, not iron deficiency (which causes anemia). Thus, statements 1 and 2 are correct.

Explanation:
Vitamin A (retinol) is essential for the synthesis of rhodopsin (visual pigment in rod cells) and maintenance of epithelial tissues. Deficiency causes night blindness (nyctalopia), xerophthalmia, and ultimately permanent blindness. Bone development is related to vitamin D and calcium. Blood clotting is vitamin K, energy metabolism involves B vitamins. Thus, vision is primarily affected.

Explanation:
Amylase (ptyalin in saliva, pancreatic amylase in intestine) hydrolyzes starch (a polysaccharide) into maltose (a disaccharide) and dextrins. Lactase breaks lactose, lipase digests lipids, protease digests proteins. Salivary amylase works at neutral pH, pancreatic amylase in the small intestine. Maltase then breaks maltose into two glucose molecules.