The hormone that increases blood calcium levels is: MCQ with Answer and Explanation

Explanation:
Cacti, xerophytes, have spiny leaves to minimize surface area and transpiration, conserving water. Thus, R correctly explains A.

Explanation:
HIV specifically infects and destroys CD4+ T cells, leading to immunodeficiency and AIDS. Without treatment, opportunistic infections occur.

Explanation:
Vitamin K is a fat-soluble vitamin required for the synthesis of clotting factors II (prothrombin), VII, IX, and X in the liver. Deficiency leads to prolonged clotting time and bleeding disorders. Vitamin A is for vision, C for collagen synthesis and antioxidant, E for antioxidant. Vitamin K is found in green leafy vegetables and synthesized by gut bacteria.