The type of cell division that creates genetic variation through crossing over is: MCQ with Answer and Explanation

Explanation:
The alveoli are the terminal, microscopic, thin-walled, highly vascularized air sacs in the lungs. They are the primary and actual sites of gas exchange, where oxygen diffuses from the inhaled air into the blood, and carbon dioxide diffuses from the blood into the alveolar air to be exhaled. Their large surface area and thin walls facilitate this diffusion.

Explanation:
The cohesion-tension theory (transpiration pull) is the primary mechanism for water ascent in tall trees. Transpiration creates negative pressure (tension) in leaves, water molecules cohere, and the column is pulled up. Root pressure and capillary action play minor roles. The cohesion of water is due to hydrogen bonds.

Explanation:
Vitamin K is essential for hepatic synthesis of clotting factors II (prothrombin), VII, IX, and X. Deficiency causes prolonged clotting time and easy bruising/bleeding. Vitamin A is for vision, B₁₂ for RBC maturation and nerve function, C for collagen synthesis. Newborns are given vitamin K to prevent hemorrhagic disease.