Explanation: Carpal bones are the eight small bones that make up the wrist (also known as the carpus) in the human skeletal system. These bones are arranged in two rows — a proximal row (closer to the forearm) and a distal row (closer to the hand). They connect the bones of the forearm (radius and ulna) to the bones of the hand (metacarpals) and allow for the flexibility and movement of the wrist. The carpals are essential for various hand motions like bending, rotation, and gripping.

Explanation: Neutron was discovered by James Chadwick in 1932. He identified the neutron as a neutral subatomic particle present in the nucleus of an atom, having a mass nearly equal to that of a proton but no electrical charge.

Explanation: Fish respire through specialized organs called gills, located on either side of their head. Gills contain thin filaments with a large surface area and rich blood supply that allow exchange of gases. When water passes over the gill membranes, oxygen diffuses into the blood and carbon dioxide diffuses out. This process enables aquatic respiration and supports survival underwater.

Explanation: The quality of petrol (gasoline) is measured by its octane number, which indicates the fuel's resistance to knocking (premature ignition) in an internal combustion engine; a higher octane number gives better performance and smoother operation.

In India, the most widely used form of renewable energy is Solar Energy. Due to the country’s tropical location, India receives abundant sunlight throughout the year, making solar power a highly viable and sustainable energy source. It is harnessed using solar panels for electricity generation and heating applications under initiatives like National Solar Mission.

• Geothermal energy: Used only in limited pilot projects.
• Hydro-electric energy: Important but not as rapidly expanding as solar.
• Thermal energy: Usually refers to non-renewable coal-based power plants.

Explanation: A barometer is an instrument used primarily for measuring atmospheric pressure. It helps in weather forecasting and determining altitudes (since atmospheric pressure decreases with height). A mercury barometer consists of a glass tube filled with mercury inverted in a mercury reservoir. When air pressure changes, the height of the mercury column changes accordingly. However, a barometer cannot measure the density of a liquid — that function is performed by a hydrometer.

Explanation: Ecology is a branch of biology that deals with the relationships of living organisms with one another and with their physical surroundings. It examines how organisms adapt to their environment, how energy flows through ecosystems, and how matter cycles within the biosphere. The term “Ecology” was first coined by Ernst Haeckel in 1866.

Explanation: The erythrocytes (RBCs) play a crucial role in the circulation of blood by carrying oxygen from the lungs to body tissues and returning carbon dioxide for exhalation. They contain hemoglobin, which binds oxygen and maintains the red color of blood. Circulation itself is driven by the heart and supported by these oxygen-carrying cells.