Explanation: The primary colours of light are Red, Green, and Blue (RGB). These are the fundamental colours that can be combined in different proportions to produce all other colours in the visible spectrum. Yellow is not a primary colour—it is a secondary colour formed by mixing red and green light. This principle of colour mixing is used in television, computer screens, and other digital displays that use RGB colour models.

Coal is a fossil fuel formed from the remains of plants that lived and died millions of years ago. Over long geological periods, heat and pressure converted these plant remains buried under soil and rock into coal. It is a major source of energy used for electricity generation, steel production, and various industrial processes. However, burning coal releases carbon dioxide, contributing to air pollution and global warming.

Other options (for context)

• Solar energy: A renewable energy source derived from sunlight, not a fossil fuel.
• Quartz: A mineral composed of silicon and oxygen, not an energy source.
• Lava: Molten rock from volcanic eruptions, not a fossil fuel.

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: Tuberculosis (TB) is not a viral disease; it is caused by a bacterium called Mycobacterium tuberculosis. In contrast, Polio, Swine flu, and Hepatitis are viral diseases caused by different types of viruses.

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: The incorrect pair is Faraday : Diffusion of gases. The diffusion of gases was studied and explained by Thomas Graham, not by Michael Faraday. Graham’s Law states that the rate of diffusion of a gas is inversely proportional to the square root of its density or molar mass. On the other hand, Michael Faraday is famous for his work on electromagnetism and electrolysis. The other pairs are correctly matched with their discoveries.

Explanation: Red light is used as a stop signal because it has the longest wavelength among visible colors, allowing it to scatter the least and remain visible from a greater distance, even in fog, rain, or dust. This ensures better visibility and safety on roads.

Explanation: Anaemia is a condition caused by a deficiency of iron in the body, leading to reduced formation of haemoglobin in red blood cells. As a result, the blood’s capacity to carry oxygen decreases, causing fatigue, weakness, dizziness, and pale skin. Iron is essential for haemoglobin synthesis, and deficiency can result from poor diet, blood loss, or malabsorption. Foods rich in iron include green leafy vegetables, liver, red meat, legumes, and jaggery.

When an ant bites, it releases formic acid (HCOOH) into the skin. This acid causes a sharp burning sensation, redness, and irritation at the site of the bite. The name “formic” comes from the Latin word “formica”, meaning ant, as the acid was first extracted from ants. The pain can be neutralized by applying a mild base like baking soda (sodium bicarbonate).

Other options (for context)

• Hydrochloric Acid: Found in the human stomach, aids digestion.
• Acetic Acid: Main component of vinegar, not involved in ant bites.
• Phosphoric Acid: Used in fertilizers and soft drinks, not produced by ants.