The process of converting atmospheric nitrogen into ammonia by microorganisms is called: MCQ with Answer and Explanation

Explanation:
Vitamin D3 (cholecalciferol) is synthesized in the epidermis of the skin when 7-dehydrocholesterol is exposed to ultraviolet B (UVB) radiation from sunlight. Vitamin B12 (cobalamin) is unique among vitamins as it contains the metal ion cobalt in its structure. Vitamin K, not Vitamin A, is essential for the synthesis of blood clotting factors. Vitamin A is crucial for vision and immunity. Thus, statements 1 and 2 are correct.

Explanation:
The pituitary, located at the base of the brain, controls many endocrine glands via its hormones, earning the name 'master gland'. Insulin is from pancreas; it is connected to hypothalamus by infundibulum.

Explanation:
Vitamin A is essential for the synthesis of rhodopsin, a visual pigment; its deficiency leads to night blindness, the inability to see in low light conditions. Vitamin B1 (thiamine) is crucial for carbohydrate metabolism; its deficiency causes beriberi, characterized by nerve and heart dysfunction, and muscle weakness. Vitamin C (ascorbic acid) is essential for collagen synthesis; its deficiency causes scurvy, characterized by bleeding gums, loose teeth, and poor wound healing. All three statements are correct.