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: Shadows are formed when an opaque object comes in the path of light. Opaque objects do not allow light to pass through them, causing a dark region called a shadow to form on the opposite side. Transparent and translucent objects allow light to pass fully or partially, so they form faint or no shadows.

Explanation: The human retina contains two types of photoreceptor cells — rods and cones. Cones are concentrated in the central part of the retina (fovea) and are sensitive to different wavelengths of light — red, green, and blue. These enable colour vision and visual acuity in bright light. Rods, on the other hand, function in dim light and provide black-and-white vision.

Explanation: The rarest blood type in the world is AB⁻ (AB negative). It is found in less than 1% of the global population. People with AB⁻ blood can receive red blood cells from all Rh-negative blood types, but they can donate only to other AB individuals.

Metals can be beaten into thin sheets because they are malleable. Malleability is a physical property of metals that allows them to withstand hammering or rolling without breaking. This property is due to the metallic bonding where positive metal ions are surrounded by a ‘sea’ of delocalized electrons, allowing the layers of atoms to slide over each other without breaking the bond. Examples of highly malleable metals include gold, silver, and aluminium.

Other options (for context)

• Ductile: Refers to the ability of metals to be drawn into wires, not beaten into sheets.
• Soft: Not true for all metals — many are hard yet malleable.
• Loosely arranged particles: Incorrect — metal atoms are closely packed in a lattice structure.

Explanation: The ATM (Automated Teller Machine) was invented by John Shepherd-Barron in 1967. He designed the first cash dispensing machine, which was installed by Barclays Bank in London, UK. The first ATM used special paper vouchers impregnated with a radioactive compound instead of plastic cards. The idea revolutionized the banking sector by allowing people to withdraw money anytime without visiting a bank counter. Modern ATMs now use magnetic or chip-based cards, PIN authentication, and networked systems for secure transactions.

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.

Graphite is used in pencils. It is a soft form of carbon that leaves a dark mark on paper due to its layered structure, where carbon atoms are arranged in sheets that slide easily over each other. Though commonly called “lead,” pencils actually contain graphite mixed with clay to adjust hardness.

• Silicon: Used in electronics, not pencils.
• Charcoal: Used in art drawing but not regular pencils.
• Phosphorous: Used in safety matches and fertilizers, not pencils.

Explanation: In household electrical wiring, all the given statements are correct: the red insulated wire is the live (phase) wire, the black insulated wire is the neutral wire, and the green insulated wire is used for earthing to ensure safety by preventing electric shocks.

Explanation: EDUSAT (Education Satellite) was launched by the Indian Space Research Organisation (ISRO) in September 2004. It was the first Indian satellite built exclusively for educational purposes, designed to provide distance learning and interactive education through satellite communication.