Which of the following statements about protein structure is correct? MCQ with Answer and Explanation

Explanation:
Simple columnar epithelium lines the stomach, intestines, and gallbladder, and functions in secretion and absorption. It often has microvilli (brush border) or goblet cells. Squamous epithelium lines alveoli and blood vessels, cuboidal kidney tubules.

Explanation:
Cytokinins are plant hormones that promote cell division, delay senescence by preventing chlorophyll degradation, and stimulate nutrient mobilization. Ethylene promotes ripening and senescence, abscisic acid promotes abscission and dormancy, auxin is involved in cell elongation. Cytokinins are synthesized in roots and transported upward. They are used to prolong the shelf life of leafy vegetables.

Explanation:
Methane (CH₄) is produced by methanogenic bacteria in anaerobic conditions of flooded rice paddies. It is a potent greenhouse gas, with a global warming potential many times that of CO₂. Nitrous oxide comes from fertilizers, CO₂ from fossil fuels, CFCs from refrigerants. Methane also comes from livestock.