Xylem is a type of vascular tissue in plants responsible for the transportation of water and dissolved minerals from the roots to the stems and leaves. The upward movement of water through xylem vessels occurs due to processes like transpiration pull, root pressure, and capillary action. Xylem also provides mechanical support to the plant.

Other options (for context)

• Food: Transported by phloem, not xylem.
• Nutrient: Minerals are carried along with water but the primary function of xylem is water transport.
• Both food and water: Incorrect — only phloem transports food; xylem transports water.

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: Rakesh Sharma was the first Indian astronaut to travel into space. He flew aboard the Soviet spacecraft Soyuz T-11 on April 3, 1984, as part of a joint mission between ISRO (Indian Space Research Organisation) and the Soviet Intercosmos program. During his space mission, he spent about 8 days aboard the Salyut-7 space station. When asked by then Prime Minister Indira Gandhi how India looked from space, he famously replied, “Saare Jahan Se Achha.”

Explanation: Windows XP is an operating system (OS) developed by Microsoft. An operating system is system software that manages computer hardware, software resources, and provides services for running application programs. Windows XP, released in 2001, was one of the most popular OS versions used for both personal and business computers. It provides a graphical user interface (GUI), multitasking, and file management capabilities.

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: The full form of OMR is Optical Mark Recognition. It is a technology used to detect marks made on specially designed paper forms, such as answer sheets in competitive exams or surveys. Candidates mark their answers by filling bubbles with dark ink or pencil, and the OMR scanner reads these marks by detecting reflected light. This process allows for fast, accurate, and automated data collection without manual checking, minimizing human errors and saving time.

Explanation: The intensity of sound is measured in decibels (dB). The decibel is a logarithmic unit that expresses the ratio of a sound’s intensity compared to a reference level (usually the faintest sound the human ear can detect, known as the threshold of hearing). The higher the decibel value, the louder the sound. For example, normal conversation is around 60 dB, traffic noise is about 80–90 dB, and sounds above 120 dB can cause pain or hearing damage.

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.

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.