One molecule of a Chlorofluorocarbon (CFC) can destroy up to 1,00,000 molecules of ozone (O₃) in the ozone layer. When CFCs reach the stratosphere, they are broken down by ultraviolet (UV) radiation, releasing chlorine atoms. Each chlorine atom acts as a catalyst in the breakdown of ozone molecules, significantly depleting the protective ozone layer that shields Earth from harmful UV rays.

Other options (for context)

• 10,000: Underestimates the destructive potential of a single CFC molecule.
• 10,00,000: Overestimates the number of ozone molecules destroyed.
• No one of the above: Incorrect — the correct answer is 1,00,000 molecules of ozone.

The Red Data Book contains information about endangered and threatened species of plants and animals. It is published by the International Union for Conservation of Nature (IUCN). The book categorizes species based on their risk of extinction, such as Critically Endangered, Endangered, Vulnerable, and Extinct. It serves as a global reference for monitoring biodiversity conservation and guiding environmental protection policies.

Other options (for context)

• All plant species: Incorrect — it includes only those plants that are endangered or threatened.
• All animal species: Incorrect — it covers only the endangered and vulnerable ones, not all animals.
• All extinct species: Incorrect — it includes species at risk of extinction, not only those already extinct.

Explanation: Ecology is a branch of biology that deals with the relationships of living organisms with one another and with their physical surroundings. It examines how organisms adapt to their environment, how energy flows through ecosystems, and how matter cycles within the biosphere. The term “Ecology” was first coined by Ernst Haeckel in 1866.

Explanation: Aerosols (such as those used in spray cans, refrigerants, and air conditioners) often contain chlorofluorocarbons (CFCs) and other halogen compounds. These chemicals rise to the stratosphere, where ultraviolet (UV) radiation breaks them down, releasing chlorine atoms. Each chlorine atom can destroy thousands of ozone (O₃) molecules, leading to ozone layer depletion. The thinning of the ozone layer allows more harmful UV rays to reach Earth, increasing the risk of skin cancer, eye damage, and affecting ecosystems.

Explanation: A lens is generally made of flint glass, which contains lead oxide. Flint glass has a higher refractive index than ordinary glass, allowing it to bend light more effectively. This property makes it ideal for manufacturing optical instruments such as lenses and prisms.

Explanation: Acupuncture is an ancient form of traditional Chinese medicine that involves the insertion of very thin needles through the skin at specific points, called acupoints. It is based on the concept of balancing the flow of life energy (Qi or Chi) through pathways in the body known as meridians. When these energy flows are blocked or imbalanced, it can cause illness or pain.

By stimulating specific acupoints, acupuncture is believed to restore the normal energy flow and help the body heal itself. It is commonly used to treat:

• Chronic pain (e.g., back, neck, and joint pain)
• Migraines and headaches
• Arthritis and muscle stiffness
• Stress and anxiety

Scientific View: Modern research suggests that acupuncture may stimulate nerves, muscles, and connective tissue, boosting the body’s natural painkillers (endorphins).

John McCarthy is regarded as the father of Artificial Intelligence (AI). He coined the term “Artificial Intelligence” in 1956 during the Dartmouth Conference, which is considered the founding event of AI as a research field. McCarthy also developed the LISP programming language, one of the earliest languages used for AI programming. His contributions laid the foundation for modern AI research, machine learning, and robotics.

Other options (for context)

• Charles Babbage: Known as the “Father of the Computer” for designing the Analytical Engine.
• Lee De Forest: Invented the triode vacuum tube, which advanced early electronics.
• J. P. Eckert: Co-inventor of ENIAC, one of the first electronic general-purpose computers.

Explanation: Brass, an alloy of copper and zinc, gets discoloured when exposed to air containing hydrogen sulphide (H₂S). The H₂S reacts with the metal surface to form a dark layer of metal sulphides (mainly copper sulphide), causing tarnishing and loss of shine.

Explanation: Alcohols are organic compounds composed of carbon (C), hydrogen (H), and oxygen (O). They are characterized by the presence of one or more hydroxyl (-OH) functional groups attached to a carbon atom. The general formula of alcohols is C_nH_2n+1OH. A common example is ethanol (C₂H₅OH), which is used in beverages, fuels, and sanitizers. The -OH group makes alcohols polar, soluble in water (especially lower alcohols), and reactive in many organic reactions.

Explanation: Human blood is maintained at a slightly alkaline pH of 7.4 (range 7.35–7.45). This balance is vital for the proper functioning of enzymes and biochemical reactions in the body. The buffer systems in blood — primarily the bicarbonate buffer system (H₂CO₃ / HCO₃⁻) — help maintain this stable pH. A small deviation from this range can lead to severe physiological disturbances.

Imbalances:

• Acidosis: pH below 7.35 — causes drowsiness, confusion, and respiratory distress.
• Alkalosis: pH above 7.45 — causes muscle twitching, irritability, and convulsions.