Explanation: Asbestos is a group of naturally occurring fibrous silicate minerals once widely used in construction and insulation. When inhaled, asbestos fibers accumulate in the lungs and pleura, leading to inflammation and scarring over years. This chronic exposure can cause asbestosis (lung fibrosis) and mesothelioma — a deadly cancer of the membrane lining the lungs (pleura) or abdomen (peritoneum).

Explanation: The femur is the single bone of the thigh region and extends from the hip joint to the knee joint. It supports the body’s weight during standing, walking, and running. The femur is the longest, heaviest, and strongest bone in the human skeleton. It articulates with the pelvic girdle at its proximal end (head of femur fits into the acetabulum of the pelvis) and with the tibia and patella at the distal end.

Average Length: Approximately 45 cm (about 1/4 of body height).

Explanation: The full form of USB is Universal Serial Bus. It is a standard interface used to connect devices such as keyboards, mice, flash drives, and printers to a computer. USB allows data transfer and power supply between connected devices.

Explanation: The phenomenon of radioactivity was discovered by the French physicist Henri Becquerel in 1896. He accidentally discovered that uranium salts emitted invisible rays that could fog photographic plates, even without sunlight. This led to the realization that certain elements spontaneously emit radiations — a property later termed as radioactivity. Subsequently, Marie and Pierre Curie expanded his work and discovered other radioactive elements like polonium and radium.

Explanation: Cobalt-60 (Co-60) is a radioactive isotope of cobalt that emits high-energy gamma rays during its decay process. It decays into Nickel-60 (Ni-60) by beta decay, releasing two strong gamma photons of energies 1.17 MeV and 1.33 MeV. Due to these intense gamma emissions, Co-60 is widely used in radiation therapy (teletherapy) for cancer treatment, as well as in industrial radiography and sterilization of medical equipment. Gamma rays have high penetration power, allowing them to destroy cancerous cells deep inside tissues.

Silver is the best conductor of heat among the given options. It efficiently transfers heat due to the presence of free electrons that move easily within its metallic structure. Because of this property, silver is used in high-quality thermal equipment and electrical contacts.

• Mercury: A metal but conducts heat less effectively than silver.
• Leather and Benzene: Poor conductors of heat (insulators).

Explanation: PROLOG (Programming in Logic) is a high-level programming language widely used in the field of Artificial Intelligence (AI) and computational linguistics. It is based on formal logic and is especially useful for solving problems involving pattern matching, rule-based reasoning, and natural language processing.

Explanation: Aurora Borealis, also known as the Northern Lights, is a natural light phenomenon visible mainly in the northern hemisphere, near the Arctic regions. It occurs when charged particles from the solar wind interact with gases like oxygen and nitrogen in the Earth's upper atmosphere (ionosphere). These collisions release energy in the form of colorful lights, usually green, pink, red, or violet. A similar phenomenon in the southern hemisphere is called the Aurora Australis or Southern Lights.

Explanation: In 1643, Italian scientist Evangelista Torricelli invented the barometer, an instrument used to measure atmospheric pressure. His mercury barometer demonstrated that air has weight and that atmospheric pressure can support a column of mercury in a glass tube.

Explanation: Fish respire through specialized organs called gills, located on either side of their head. Gills contain thin filaments with a large surface area and rich blood supply that allow exchange of gases. When water passes over the gill membranes, oxygen diffuses into the blood and carbon dioxide diffuses out. This process enables aquatic respiration and supports survival underwater.