Explanation: Antibodies (also called immunoglobulins) are specialized proteins produced by B-lymphocytes (a type of white blood cell) in response to the presence of foreign substances known as antigens (such as bacteria, viruses, or toxins). These antibodies recognize and bind specifically to the antigens to neutralize or destroy them, helping the body fight infections and build immunity. Antibodies are a vital part of the immune system and form the basis for vaccines and disease resistance.

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: Cadmium (Cd) is a toxic heavy metal released from industrial waste, batteries, and mining processes. When it enters the food chain (especially through contaminated rice or water), it accumulates in the body and affects the kidneys, causing protein loss in urine and kidney failure. It is also associated with Itai-Itai disease in Japan, characterized by kidney damage and brittle bones.

Explanation: To read small letters, a convex lens (converging lens) with a short focal length such as 5 cm is used as a magnifying glass. It produces an enlarged, upright, and virtual image of the object, making tiny text appear bigger and clearer to the eye.

Explanation: Sound travels fastest in steel because it is a solid material where the particles are packed very closely together. Sound waves need a medium to travel, and their speed depends on how quickly vibrations can pass from one particle to another. In solids, particles are tightly bound, so vibrations are transmitted more efficiently. In contrast, sound travels slower in liquids and slowest in gases. It cannot travel through a vacuum because there are no particles to carry the vibrations.

Explanation: Albert Einstein received the Nobel Prize in Physics in 1921 for his discovery of the photoelectric effect, not for his famous theory of relativity. In the photoelectric effect, when light of a certain frequency falls on a metal surface, it emits electrons. Einstein explained this phenomenon by proposing that light is made up of discrete packets of energy called photons. The energy of each photon is given by E = hν, where h is Planck’s constant and ν is the frequency of light. This discovery laid the foundation for quantum physics and modern electronics.

Explanation: Sound waves in air are longitudinal waves, meaning the particles of the medium vibrate back and forth in the same direction as the wave travels. These waves require a material medium (like air, water, or solids) for propagation and cannot travel through a vacuum.

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.

Explanation: The blue colour of the sky is due to the scattering of sunlight by molecules and small particles in the Earth's atmosphere. Shorter wavelengths of light (blue and violet) are scattered more than longer wavelengths (red and yellow). Since our eyes are more sensitive to blue light, the sky appears blue.