The average life span of human red blood cells is about: MCQ with Answer and Explanation

Explanation:
All three are correct: A is fat-soluble, C is water-soluble, D is synthesized in skin from cholesterol derivatives upon UV exposure.

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:
Transpiration is the evaporative loss of water from the aerial parts of plants, primarily through stomata. It creates transpiration pull, aiding water and mineral transport. Guttation is loss of liquid water droplets from hydathodes. Evaporation is a physical process from any surface. Condensation is change from vapour to liquid. Transpiration also cools the plant.