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: Lysosomes are known as the ‘suicidal bags’ or ‘disposal units’ of the cell because they contain powerful digestive enzymes capable of breaking down worn-out cell parts, foreign substances, and even the entire cell when it becomes damaged or obsolete.

Explanation: A rainbow is formed due to the dispersion of sunlight into its constituent colors and total internal reflection inside water droplets in the atmosphere. The light entering a droplet is refracted, reflected internally, and then refracted again as it exits, producing the beautiful spectrum of colors.

Running water is the source of hydel power (also called hydroelectric power). The energy of flowing or falling water is converted into electrical energy using turbines and generators in dams. It is a renewable, clean, and sustainable source of energy widely used in India and worldwide.

• Thermal power: Generated by burning coal or other fuels.
• Nuclear power: Produced from nuclear fission reactions.
• None of the above: Incorrect — running water directly produces hydel power.

Explanation: Marijuana is a psychoactive drug obtained from the female inflorescence (flowering tops) of the Cannabis sativa plant. It contains the active compound tetrahydrocannabinol (THC), which affects the central nervous system and alters mood and perception.

Explanation: Vitamins are classified into two categories based on their solubility — fat-soluble and water-soluble. Vitamin C (ascorbic acid) and the B-complex vitamins are water-soluble, meaning they dissolve in water and are not stored in the body. Therefore, they must be consumed regularly through diet. Deficiency of Vitamin C causes scurvy, characterized by bleeding gums and delayed wound healing.

Explanation: Seismology is the branch of geophysics that deals with the study of earthquakes and the propagation of seismic waves through the Earth. Scientists who study earthquakes are called seismologists. Seismology helps in understanding the origin, intensity, and effects of earthquakes, as well as the internal structure of the Earth. The intensity of an earthquake is measured using instruments like the seismograph and scales such as the Richter scale or Moment Magnitude scale.

Explanation: Producer gas is a mixture of flammable gases such as carbon monoxide (CO) and hydrogen (H₂), along with nonflammable gases like nitrogen (N₂) and carbon dioxide (CO₂). It is produced by the partial combustion of carbon-containing fuels (like coal or coke) with air and steam, and is used as a fuel in industrial furnaces.

Explanation: Cerebral malaria is a severe neurological complication of malaria infection caused by Plasmodium falciparum. The parasite infects red blood cells, making them sticky and causing them to block small blood vessels in the brain. This leads to high fever, seizures, coma, and can be fatal if untreated. Transmission occurs through the bite of an infected female Anopheles mosquito.

Explanation: The King Cobra (Ophiophagus hannah) is the world’s longest venomous snake and the only snake species that builds a nest to lay its eggs. The female collects leaves, twigs, and debris to construct a mound-like nest, usually near dense vegetation or fallen logs. She lays about 20–40 eggs in the nest and guards them aggressively until they hatch, showing remarkable parental care — a rare behavior among reptiles.

Once the eggs are about to hatch, the female leaves the nest to avoid eating her own offspring, as King Cobras are carnivorous and feed mainly on other snakes.