Explanation: The incorrect pair is Faraday : Diffusion of gases. The diffusion of gases was studied and explained by Thomas Graham, not by Michael Faraday. Graham’s Law states that the rate of diffusion of a gas is inversely proportional to the square root of its density or molar mass. On the other hand, Michael Faraday is famous for his work on electromagnetism and electrolysis. The other pairs are correctly matched with their discoveries.

Explanation: Human blood is maintained at a slightly alkaline pH of 7.4 (range 7.35–7.45). This balance is vital for the proper functioning of enzymes and biochemical reactions in the body. The buffer systems in blood — primarily the bicarbonate buffer system (H₂CO₃ / HCO₃⁻) — help maintain this stable pH. A small deviation from this range can lead to severe physiological disturbances.

Imbalances:

• Acidosis: pH below 7.35 — causes drowsiness, confusion, and respiratory distress.
• Alkalosis: pH above 7.45 — causes muscle twitching, irritability, and convulsions.

Sustainable Development refers to growth that meets the needs of the present without compromising the ability of future generations to meet their own needs. It aims to balance economic progress, social equity, and environmental protection by conserving natural resources and reducing pollution for long-term ecological stability.

• Green economy: Focuses mainly on eco-friendly industries.
• Holistic development: Emphasizes overall human and social growth.
• Subsistence agriculture: Involves farming mainly for self-consumption.

Explanation: The speed of light is maximum in a vacuum (approximately 3 × 10⁸ m/s) and decreases as it passes through denser media. Among the given options — vacuum, air, water, and glass — light travels slowest in glass because glass has the highest refractive index (around 1.5). The greater the refractive index, the slower the light travels. This slowing down of light causes refraction, or bending of light, when it passes from one medium to another.

Explanation: The main constituents of biogas are methane (CH₄) and carbon dioxide (CO₂). Biogas is produced through the anaerobic decomposition of organic matter such as animal dung and plant waste. Methane acts as the primary combustible component, making biogas an efficient and renewable source of energy.

Explanation: The elements Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N) — collectively known as CHON — were primarily responsible for the origin of life on Earth. These elements are the basic building blocks of all biological molecules such as proteins, nucleic acids, carbohydrates, and lipids. Early Earth's atmosphere contained these elements in gaseous forms (like CH₄, NH₃, H₂, and H₂O), which combined under lightning and UV radiation to form simple organic compounds — a process explained by the Miller–Urey experiment.

Explanation: All enzymes are proteins (except a few RNA-based enzymes called ribozymes). Enzymes act as biological catalysts that speed up chemical reactions in living organisms without being consumed in the process. They work by lowering the activation energy of reactions, ensuring that metabolic processes occur efficiently at normal body temperatures. Each enzyme is specific to a particular substrate, forming an enzyme-substrate complex to carry out its function effectively.

Explanation: The sour taste of a lemon is due to the presence of citric acid. Citric acid is a weak organic acid found naturally in citrus fruits such as lemons, oranges, and limes. It gives them their characteristic tangy flavor and also acts as a natural preservative.

Explanation: The intensity and magnitude of an earthquake are measured using a scientific instrument called a seismograph. It records the vibrations or seismic waves produced by earthquakes. The data obtained from a seismograph are used to calculate the earthquake’s strength on scales such as the Richter Scale or the Moment Magnitude Scale. The seismogram (the recorded graph) shows the amplitude and duration of the waves, helping scientists locate the earthquake’s epicenter and determine its severity.