Explanation: The Montreal Protocol, signed in 1987, is an international agreement aimed at protecting the ozone layer by phasing out the production and use of ozone-depleting substances (ODS) such as chlorofluorocarbons (CFCs) and halons. It is one of the most successful environmental treaties in history.

Explanation: SONAR (Sound Navigation and Ranging) is a system used in ships and submarines to determine the depth of the ocean or to locate underwater objects. It works by sending sound waves into the water and measuring the time taken for the echo to return after reflecting from the seabed or any object.

Explanation: Among the given particles, the proton is the heaviest. A proton is a positively charged subatomic particle found in the nucleus of an atom, with a mass of approximately 1.672 × 10⁻²⁷ kg. Although the neutron is slightly heavier than a proton, in most general questions like this one, protons are considered heavier in context when compared with electrons and neutrinos. Electrons are much lighter, with a mass about 1/1836 that of a proton, while neutrinos are nearly massless and electrically neutral.

Sodium bicarbonate (NaHCO₃), also known as baking soda, is used in fire extinguishers. When heated, it decomposes to produce carbon dioxide (CO₂), which displaces oxygen and helps smother the fire. It is especially effective for extinguishing electrical and small grease fires.

• Sodium carbonate: Used in glass and soap making, not for fire control.
• Sodium nitrate: An oxidizing agent, not suitable for extinguishing fires.
• Sodium sulphate: Used in detergents and paper making, not in fire extinguishers.

All of the above are examples of static electricity. Static electricity is the result of the accumulation of electric charges on the surface of objects. When materials like glass, silk, ebonite, or wool are rubbed together, electrons are transferred, creating a charge imbalance. Similarly, lightning is a large-scale natural discharge of static electricity between clouds and the Earth.

• Glass rod & silk cloth: Positive and negative charges develop.
• Ebonite rod & wool: Negative charge accumulates on ebonite.
• Lightning: Discharge of atmospheric static electricity.

Explanation: Sugarcane (Saccharum officinarum) is a tall, jointed, perennial grass belonging to the family Poaceae. It has thick stems rich in sucrose, which is extracted to produce sugar. The plant reproduces mainly through stem cuttings (vegetative propagation). Its structure and growth habit are similar to other grasses like maize and bamboo.

Explanation: Penicillin was discovered accidentally by Alexander Fleming in 1928 when he observed that a fungal mold, Penicillium notatum, inhibited the growth of Staphylococcus bacteria in his culture plates. Penicillin became the first antibiotic used to treat bacterial infections and saved millions of lives during World War II. Later, scientists like Howard Florey and Ernst Boris Chain developed methods for its large-scale production.

Explanation: The term "Ozone hole" does not mean an actual hole but refers to a significant decrease in the thickness of the ozone layer in the Earth's stratosphere. This thinning occurs mainly over the Antarctic region during spring (September–November) due to chemical reactions involving chlorofluorocarbons (CFCs) and other ozone-depleting substances. These chemicals release chlorine and bromine atoms, which destroy ozone (O₃) molecules. The thinning allows more harmful ultraviolet (UV) radiation to reach the Earth's surface, causing health and environmental hazards.