Assertion (A): Bacteria can be killed by antibiotics like penicillin. Reason (R): Penicillin inhibits the synthesis of bacterial cell wall. MCQ with Answer and Explanation

Explanation:
Vitamin B₆ (pyridoxine, pyridoxal, pyridoxamine) is a coenzyme (pyridoxal phosphate, PLP) for many enzymes involved in amino acid metabolism, including transaminases and decarboxylases. B₁ acts in carbohydrate metabolism, B₂ in redox reactions, B₁₂ in methylation and DNA synthesis.

Explanation:
Thermoregulation uses negative feedback mechanisms: when body temperature rises, sweating and vasodilation cool the body; when it falls, shivering and vasoconstriction generate and conserve heat. Negative feedback counteracts deviations from a set point. Positive feedback amplifies a change (e.g., labor contractions).

Explanation:
Deforestation, the large-scale removal of trees and vegetation, exposes the topsoil to wind and water, leading to severe soil erosion and loss of fertility. Afforestation, the planting of trees in barren areas, increases biomass and helps mitigate global warming by sequestering atmospheric carbon dioxide through photosynthesis. Most plastics are synthetic polymers that are non-biodegradable, meaning they cannot be broken down by natural biological processes and persist in the environment for centuries, causing pollution. All statements are correct.