Explanation: Organic farming is an agricultural method that emphasizes the use of natural inputs and eco-friendly techniques. It avoids chemical fertilizers, pesticides, and genetically modified organisms (GMOs). Instead, it uses organic manures (compost, green manure, and farmyard manure), crop rotation, and biological pest control to maintain soil health and productivity. Chemical fertilizers are excluded because they degrade soil quality and harm beneficial soil organisms over time.

Explanation: Acids do not turn red litmus to blue; instead, they turn blue litmus paper red. Acids are sour in taste, corrosive in nature, and have a pH value less than 7. Therefore, the statement that acids turn red litmus to blue is incorrect.

Explanation: The ozone layer is located in the stratosphere, which is the second layer of the Earth’s atmosphere, lying above the troposphere and extending from about 10 km to 50 km above the Earth’s surface. The ozone layer contains a high concentration of ozone gas (O₃), which absorbs most of the Sun’s harmful ultraviolet (UV) radiation. This protective shield prevents genetic damage, skin cancer, and other harmful effects on living organisms.

Explanation: The major cause of global warming is the increasing concentration of carbon dioxide (CO₂) in the atmosphere. CO₂ is a greenhouse gas that traps heat radiating from the Earth's surface, preventing it from escaping into space — a phenomenon known as the greenhouse effect. Human activities such as the burning of fossil fuels, deforestation, and industrial emissions have significantly increased CO₂ levels, leading to a rise in the Earth’s average temperature, melting of glaciers, rising sea levels, and climate change.

The full form of LAN is Local Area Network. It is a network that connects computers and devices within a limited geographical area such as a home, office, school, or building. LANs enable data sharing, resource sharing (like printers or internet connections), and communication between connected devices. Common technologies used in LANs include Ethernet and Wi-Fi.

Other options (for context)

• Line Area Network: Incorrect — not a recognized networking term.
• Linear Area Network: Incorrect — there is no such standard network type.
• Land Area Network: Incorrect — misinterpretation of LAN abbreviation.

Explanation: Dehydration happens when the body loses excessive water through sweating, vomiting, diarrhea, or inadequate fluid intake. It disturbs the balance of electrolytes and reduces blood volume, leading to symptoms such as thirst, dry mouth, fatigue, and dizziness. To prevent dehydration, oral rehydration solutions (ORS) or adequate water intake are essential.

Adolf Gaston Eugen Fick, a German physiologist, invented the first successful contact lens in 1888. His design consisted of a glass lens that covered the entire eye, resting on the sclera (the white part of the eye). Though bulky and uncomfortable by today’s standards, it laid the foundation for modern soft and gas-permeable contact lenses used in vision correction and cosmetics.

Other options (for context)

• Enrico Fermi: Known for his work in nuclear physics and development of the first nuclear reactor.
• Sandford Fleming: Introduced the concept of standard time zones.
• Benoit Fourneyron: Invented the water turbine, not related to optics or vision correction.

Explanation: White blood cells (WBCs), also known as leukocytes, are responsible for producing the immune response in the human body. They defend against infections by attacking bacteria, viruses, and other foreign invaders, helping to maintain the body’s immunity.

Explanation: An anemometer is a meteorological instrument used to measure wind speed and direction. It is an essential tool in weather stations, aviation, and marine forecasting.

Working Principle: The cup anemometer has three or four cups that rotate with the wind. The rotation speed is proportional to wind velocity. Advanced types also detect wind direction.

Types of Anemometers:

• Cup: Measures wind speed using rotating cups.
• Vane: Measures both speed and direction.
• Hot-wire: Uses heat loss to measure air flow.
• Ultrasonic: Uses sound waves for precise measurement.

Sustainable Development refers to growth that meets the needs of the present without compromising the ability of future generations to meet their own needs. It aims to balance economic progress, social equity, and environmental protection by conserving natural resources and reducing pollution for long-term ecological stability.

• Green economy: Focuses mainly on eco-friendly industries.
• Holistic development: Emphasizes overall human and social growth.
• Subsistence agriculture: Involves farming mainly for self-consumption.