Explanation: Rickets is a bone disease caused by the deficiency of Vitamin D in children. Vitamin D is essential for the proper absorption of calcium and phosphorus from the intestine, which are vital for healthy bone formation. Its deficiency leads to weak and soft bones, resulting in deformities such as bowed legs and knock knees. The adult form of this disease is known as osteomalacia. Vitamin D can be obtained from sunlight, fish oil, eggs, and fortified milk.

The Green Muffler technique is used to control noise pollution. It involves planting dense rows of trees and shrubs around roads, industrial areas, and public places. The vegetation acts as a natural sound barrier by absorbing, deflecting, and refracting sound waves, thereby reducing the intensity of noise reaching nearby areas. Common plants used for green mufflers include Neem, Ashoka, Ficus, and Cassia.

Other options (for context)

• Air pollution: Controlled by measures like emission filters and afforestation, but not directly by green mufflers.
• Soil pollution: Managed by waste treatment and reduced chemical use, not vegetation barriers.
• Water pollution: Controlled by sewage treatment and reducing industrial discharge, not by plants as mufflers.

Explanation: Lysergic acid diethylamide (LSD) was discovered by Dr. Albert Hofmann, a Swiss chemist, in 1938 at the Sandoz Laboratories in Switzerland. LSD is a powerful hallucinogenic compound derived from lysergic acid, which occurs in the fungus Claviceps purpurea (ergot) that grows on rye. Hofmann accidentally discovered its psychological effects in 1943 when he absorbed a small amount through his skin, leading to vivid visual hallucinations. LSD acts on serotonin receptors in the brain and profoundly alters perception and mood.

A rocket functions based on Newton’s Third Law of Motion, which states that “for every action, there is an equal and opposite reaction.” The rocket expels gases downward at high speed (action), and in response, the rocket is propelled upward (reaction). This principle enables space rockets to move even in the vacuum of space where no air resistance exists.

• Newton’s First Law: Deals with inertia, not propulsion.
• Newton’s Second Law: Explains force and acceleration but doesn’t directly describe rocket thrust.

Explanation: Mucor is not a biofertilizer; it is a saprophytic fungus that grows on decaying organic matter. Biofertilizers are living microorganisms that enhance soil fertility by fixing atmospheric nitrogen or solubilizing nutrients. Examples include Rhizobium, Azotobacter, and Anabaena.

The average distance between the Earth and the Sun is approximately 150 million kilometers (or about 1 Astronomical Unit – 1 AU). This distance serves as a standard unit of measurement for describing distances within our solar system. Despite slight variations due to Earth's elliptical orbit, this average remains nearly constant and is crucial for maintaining suitable conditions for life on Earth.

Other options (for context)

• 15 Million km: Far too close — the Earth would be extremely hot and uninhabitable.
• 90 Million km: Shorter than the actual average distance.
• 900 Million km: Much greater — about six times the real distance, closer to Saturn’s orbit.

Explanation: Bryology is the branch of botany that deals with the study of bryophytes, which include mosses and liverworts. These are small, non-vascular plants that typically grow in moist and shady environments.

Explanation: Sound waves with frequencies below 20 Hz are called infrasonic waves. These waves are inaudible to the human ear but can be produced by natural phenomena such as earthquakes, volcanic eruptions, and ocean waves.