Vitamin-B complex and Vitamin-C are water-soluble vitamins. This means they dissolve easily in water and are not stored in the body; hence, they must be consumed regularly through diet. Excess amounts of these vitamins are excreted through urine. Vitamin-B complex includes B₁ (Thiamine), B₂ (Riboflavin), B₃ (Niacin), B₆, B₁₂, and others that play key roles in metabolism and energy production. Vitamin-C (Ascorbic acid) helps in collagen formation, boosts immunity, and acts as an antioxidant.

Other options (for context)

• Vitamin-A & Vitamin-B: Vitamin-A is fat-soluble, while Vitamin-B is water-soluble.
• Vitamin-C & Vitamin-D: Vitamin-C is water-soluble, but Vitamin-D is fat-soluble.
• Vitamin-A & Vitamin-K: Both are fat-soluble vitamins.

Dynamite was invented by Alfred Nobel in 1867. He was a Swedish chemist, engineer, and industrialist who discovered that nitroglycerin could be stabilized by mixing it with an absorbent material like diatomaceous earth, making it safer to handle and transport. This invention revolutionized the mining and construction industries. In his later years, Alfred Nobel established the Nobel Prizes using the wealth he accumulated from his inventions.

Other options (for context)

• J. B. Dunlop: Invented the pneumatic rubber tyre.
• James Simons: A mathematician and hedge fund manager, not an inventor.
• Peter Hargreaves: Not related to any major scientific invention; possibly confused with James Hargreaves, who invented the Spinning Jenny.

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.

Explanation: Uranium-235 (U-235) is the isotope used for the production of atomic energy because it is fissionable. When bombarded with neutrons, U-235 undergoes nuclear fission, releasing a large amount of energy along with additional neutrons, which sustain the chain reaction in nuclear reactors and atomic bombs.

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.

Nitrous oxide (N₂O) is an anaesthetic gas, commonly known as laughing gas. It is used in dentistry and minor surgeries to induce mild anesthesia and relaxation. It acts quickly and wears off rapidly, making it safe for short medical procedures.

• Nitrogen dioxide: A toxic air pollutant, not used as anesthesia.
• Nitric oxide: A signaling molecule in the body, not an anesthetic.
• Nitrogen: An inert gas, does not induce anesthesia.

Explanation: An F1 (Formula One) car is primarily made of carbon fibre, a lightweight yet extremely strong and durable material. Carbon fibre provides high strength-to-weight ratio, excellent rigidity, and improved safety — essential for achieving high speeds and ensuring driver protection in racing conditions.

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: Natural gas is a non-renewable source of energy because it is formed from fossilized organic matter over millions of years and cannot be replenished quickly. In contrast, geothermal energy, flowing water, and biomass are renewable as they can be naturally regenerated over short periods.

Explanation: The onion is a modified underground stem called a bulb. It consists of a short, disc-like stem (the basal plate) surrounded by concentric fleshy leaf bases that store food. The roots emerge from the underside of the basal plate, and new shoots grow from the center. Thus, the onion bulb serves as a storage organ for nutrients and helps in vegetative propagation.