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: In 1643, Italian scientist Evangelista Torricelli invented the barometer, an instrument used to measure atmospheric pressure. His mercury barometer demonstrated that air has weight and that atmospheric pressure can support a column of mercury in a glass tube.

Explanation: Bilirubin and Biliverdin are yellow and green bile pigments respectively, found in the bile secreted by the liver. These pigments are produced during the breakdown of hemoglobin from old red blood cells (RBCs) in the liver and spleen. Biliverdin (green pigment) is first formed from the heme part of hemoglobin and is then reduced to bilirubin (yellow pigment). The bile containing these pigments helps in the digestion and emulsification of fats. Excess bilirubin in the blood causes jaundice, leading to a yellowing of the skin and eyes.

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: An endoscope works on the principle of total internal reflection of light. It uses optical fibers to transmit light into the body and carry the reflected image back to the observer. This allows physicians to view internal organs without surgery.

The ozone hole leads to an increase in ultraviolet (UV) radiation reaching the Earth's surface. The depletion of the ozone layer, caused by chemicals like CFCs (chlorofluorocarbons), reduces its ability to block harmful UV rays. This can result in health issues such as skin cancer, cataracts, and also harm to crops and marine ecosystems.

• Acid rain: Caused by sulphur and nitrogen oxides, not ozone depletion.
• Global warming: Caused by greenhouse gases trapping heat.
• Greenhouse effect: Natural process intensified by CO₂, not related to ozone loss.

Coal is a fossil fuel formed from the remains of plants that lived and died millions of years ago. Over long geological periods, heat and pressure converted these plant remains buried under soil and rock into coal. It is a major source of energy used for electricity generation, steel production, and various industrial processes. However, burning coal releases carbon dioxide, contributing to air pollution and global warming.

Other options (for context)

• Solar energy: A renewable energy source derived from sunlight, not a fossil fuel.
• Quartz: A mineral composed of silicon and oxygen, not an energy source.
• Lava: Molten rock from volcanic eruptions, not a fossil fuel.