Explanation: The statement “Exercise does not help in managing psychological discomfort” is incorrect. Regular physical exercise helps reduce stress, anxiety, and depression by releasing endorphins — the body’s natural mood enhancers. It also improves overall mental health, cardio-respiratory fitness, reduces the risk of diabetes, and strengthens bones.

Explanation: LCD stands for Liquid Crystal Display. It is a flat-panel display technology commonly used in televisions, computer monitors, calculators, and smartphones. LCDs use liquid crystals that modulate light to produce images when an electric current is applied.

Explanation: Shadows are formed when an opaque object comes in the path of light. Opaque objects do not allow light to pass through them, causing a dark region called a shadow to form on the opposite side. Transparent and translucent objects allow light to pass fully or partially, so they form faint or no shadows.

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 heavy stone appears lighter when immersed in water because of the upward pressure or buoyant force exerted by the water. This phenomenon is explained by Archimedes’ Principle, which states that a body immersed in a fluid experiences an upward force equal to the weight of the fluid displaced by it. The greater the volume of the object submerged, the greater the buoyant force acting on it. Hence, the stone seems lighter in water, even though its actual mass remains the same.

Explanation: Uranium-235 (U-235) is the isotope used for the production of atomic energy because it is fissionable. When bombarded with neutrons, U-235 undergoes nuclear fission, releasing a large amount of energy along with additional neutrons, which sustain the chain reaction in nuclear reactors and atomic bombs.

Explanation: Water shows an unusual property known as anomalous expansion. Its density is maximum at 4°C. When cooled from higher temperatures, water contracts till 4°C, becoming denser. Below 4°C, it expands instead of contracting, so its density decreases. This property allows ice to float and prevents water bodies from freezing solid, protecting aquatic life during winters.

Explanation: In fused (molten) sodium chloride, electric current passes due to the presence of free ions. When solid NaCl is melted, it dissociates into Na⁺ and Cl⁻ ions, which can move freely and conduct electricity. In the solid state, these ions are fixed in the crystal lattice, so it does not conduct electricity.

Explanation: Photosynthesis is the process by which green plants, algae, and some bacteria use sunlight to convert carbon dioxide (CO₂) and water (H₂O) into glucose (C₆H₁₂O₆) and oxygen (O₂). This process takes place in the chloroplasts of plant cells, which contain the green pigment chlorophyll that captures solar energy.

Chemical Equation:

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Thus, plants are known as autotrophs because they produce their own food using light energy — a process vital for sustaining all life on Earth.