Explanation: Rickets is a bone disease caused by the deficiency of Vitamin D in children. Vitamin D is essential for the proper absorption of calcium and phosphorus from the intestine, which are vital for healthy bone formation. Its deficiency leads to weak and soft bones, resulting in deformities such as bowed legs and knock knees. The adult form of this disease is known as osteomalacia. Vitamin D can be obtained from sunlight, fish oil, eggs, and fortified milk.

Explanation: Natural gas is a non-renewable source of energy because it is formed from fossilized organic matter over millions of years and cannot be replenished quickly. In contrast, geothermal energy, flowing water, and biomass are renewable as they can be naturally regenerated over short periods.

The Biome is the largest ecological unit. It includes several ecosystems that share similar climate, vegetation, and animal life. Examples include tundra, desert, rainforest, and grassland. A biome represents a major community of living organisms adapted to a specific environment over large geographical areas.

• Organism: An individual living being.
• Population: A group of the same species living in an area.
• Ecosystem: Includes both living and non-living components, but multiple ecosystems together form a biome.

Explanation: A mirage is an optical illusion caused by both refraction and total internal reflection of light. It occurs when light rays bend due to temperature variations in air layers near the ground, creating the illusion of water or a reflected image on hot surfaces like roads or deserts.

Explanation: When a bus starts suddenly, the passengers tend to lean backward due to the inertia of rest. Inertia is the tendency of a body to resist any change in its state of motion or rest. The lower part of the passenger’s body moves forward with the bus as it starts, but the upper part of the body tends to remain at rest momentarily. This makes the passenger appear to fall backward relative to the bus. It is a clear example of Newton’s First Law of Motion.

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: The chemical name of baking powder is sodium bicarbonate (NaHCO₃), also known as baking soda. It is a mild alkali used in cooking and baking as a leavening agent. When heated or mixed with an acid (like vinegar, lemon juice, or cream of tartar), it decomposes to release carbon dioxide gas (CO₂). The bubbles of CO₂ make the dough rise and become soft and spongy. In commercial baking powder, sodium bicarbonate is often mixed with a weak acid and a drying agent.

The aorta is the largest artery in the human body. It originates from the left ventricle of the heart and distributes oxygenated blood to all parts of the body through its various branches. The aorta has thick, elastic walls that can withstand the high pressure of blood pumped directly from the heart. It is divided into parts such as the ascending aorta, aortic arch, and descending aorta.

Other options (for context)

• Capillary: The smallest blood vessels where exchange of gases and nutrients occurs.
• Vena cava: The largest vein, not an artery; it carries deoxygenated blood back to the heart.
• Pulmonary vein: Carries oxygenated blood from the lungs to the heart but is not the largest vessel.

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.