Explanation: Sodium (Na⁺) plays a crucial role in the transmission of nerve impulses in the human body. Nerve cells (neurons) transmit signals through an electrochemical process known as the nerve impulse or action potential. During this process, the movement of sodium (Na⁺) and potassium (K⁺) ions across the nerve cell membrane generates an electrical charge. The rapid influx of sodium ions causes depolarization, which allows the nerve impulse to travel along the neuron, ensuring proper communication between the brain, spinal cord, and body.

Explanation: Inside a sealed pressure cooker, the pressure is higher than atmospheric pressure, which raises the boiling point of water to about 121℃. This allows food to cook faster because water and steam reach higher temperatures than at normal atmospheric pressure.

Explanation: Athlete’s foot, scientifically known as Tinea pedis, is a fungal infection caused mainly by dermatophytes such as Trichophyton species. It thrives in warm, moist areas like the skin between the toes. Symptoms include itching, scaling, redness, and sometimes blistering. It spreads easily in communal areas like locker rooms and swimming pools. Proper hygiene and antifungal treatment can prevent and cure the infection.

Explanation: When a sound wave travels from one medium to another, its frequency remains unchanged. However, its wavelength and speed change depending on the properties of the new medium. The constant frequency ensures that the sound maintains the same pitch.

Explanation: The heart is enclosed in a double-layered protective membrane called the pericardium. The outer fibrous layer protects the heart and anchors it within the chest cavity, while the inner serous layer secretes pericardial fluid that reduces friction during heartbeats. This fluid-filled sac ensures smooth and cushioned movement of the heart as it contracts and relaxes continuously.

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.

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 concave lens always forms a virtual, erect, and diminished image, regardless of the position of the object. The image formed appears on the same side of the lens as the object and is used in devices like spectacles for correcting short-sightedness (myopia).

Explanation: The Olive Ridley turtle (Lepidochelys olivacea) is the smallest and most abundant species of sea turtle found primarily in warm and tropical waters, including the Indian Ocean. It is named for the olive color of its shell. These turtles are famous for their unique mass nesting phenomenon known as “arribada”, where thousands of females come ashore simultaneously to lay eggs. In India, large nesting sites are found along the coast of Odisha, especially at Gahirmatha Beach and the Rushikulya River mouth.