Unit 5: Green Skills - IV

Correct answer: D. Wind

The governing concept is the conversion of kinetic energy into electrical energy. Moving air possesses kinetic energy; when it flows across turbine blades, the blades rotate. The rotating shaft drives a generator, which converts mechanical energy into electricity. Thus, option D is correct because wind is the natural source directly used by a wind turbine. Coal and natural gas are fossil fuels used in combustion-based power generation, not the source described here. Sunlight is the source of solar energy, although uneven heating by sunlight helps create winds. Wind is therefore classified as a renewable energy source when managed appropriately.

Correct answer: B. Organic waste

The governing concept is biological decomposition of organic matter. Composting uses biodegradable materials such as food scraps, fruit and vegetable peels, grass, and dry leaves. Bacteria, fungi, and other decomposers break these materials into simpler substances under suitable conditions of moisture, air, and temperature. The resulting compost can improve soil structure and provide organic nutrients. Therefore, option B is correct. Glass pieces, an iron nail, and a plastic bottle are not suitable compost ingredients because they do not decompose like organic matter; they should instead be separated for reuse, recycling, or safe disposal. Composting also reduces the amount of wet waste sent to landfills.

Correct answer: A. Waste that can be decomposed naturally by microorganisms

The governing concept is biodegradation, in which living decomposers such as bacteria and fungi break complex organic material into simpler substances through natural processes. Option A gives the correct definition: biodegradable waste can be decomposed by microorganisms under suitable environmental conditions. Food leftovers, leaves, and many fruit peels are common examples. Option C describes a major feature of non-biodegradable waste, not biodegradable waste. Options B and D are not definitions: biodegradable material need not be made of metal, and it is not necessarily poisonous. Correct classification helps communities separate wet organic waste for composting and manage other waste safely.

Correct answer: D. Plastic bag

The governing concept is the ability of microorganisms to decompose a material naturally. A plastic bag is non-biodegradable because ordinary bacteria and fungi do not break it down quickly into harmless natural substances; it can persist in the environment and contribute to litter and pollution. Therefore, option D is correct. Banana peels, dry leaves, and vegetable peels are organic materials that can be decomposed by microorganisms and may be converted into compost under suitable conditions. This distinction supports waste segregation: organic waste should be composted, while plastic should be reduced, reused, collected, and sent for appropriate recycling or disposal.

Correct answer: A. Damaged or unusable electronic devices

The governing concept is the classification of discarded electrical and electronic equipment. E-waste is formed when devices or their components become old, damaged, obsolete, or unusable and are thrown away. Examples include mobile phones, computers, televisions, printers, batteries, chargers, and circuit boards. Therefore, option A is correct. Dry flowers are organic waste, fresh fruits are usable biological material, and drinking water is not waste of an electronic nature. E-waste requires responsible collection because some components may contain recoverable metals and hazardous substances. It should not be burned or mixed casually with household waste; authorised recycling helps recover materials and reduce environmental harm.

Correct answer: B. Switching off lights when not needed

The governing concept is energy conservation: providing the same useful service while avoiding unnecessary energy consumption. Switching off lights when they are not needed directly prevents electricity from being wasted, so option B is correct. Leaving lights on during daylight, running a fan in an empty room, and keeping unused devices switched on all consume energy without providing a useful benefit. Such small actions can reduce electricity demand, lower household expenses, and indirectly reduce emissions when electricity is generated from fossil fuels. Good conservation habits include using daylight, switching off appliances, and unplugging equipment when appropriate. The key test is whether the action prevents avoidable use.

Correct answer: C. Turning off the tap while brushing teeth

The governing concept is water conservation, which means using water carefully and preventing avoidable loss. Turning off the tap while brushing stops water from flowing when it is not needed, so option C is correct. Leaving a tap running and allowing a storage tank to overflow waste usable water. Dumping waste into water does not conserve it; it causes pollution and may make the water unsafe for people and ecosystems. Other conservation practices include repairing leaks, using only the required amount, collecting rainwater where suitable, and reusing relatively clean water for plants. The correct option is the one that reduces unnecessary consumption without creating another environmental problem.

Correct answer: D. It can reduce the number of private vehicles and air pollution

The governing concept is shared, efficient transportation. A bus, metro, or train can carry many passengers in one vehicle, so fewer separate cars or two-wheelers may be required for the same number of journeys. This can reduce fuel use per passenger, traffic congestion, and vehicle-related air pollution, making option D correct. The exact environmental benefit depends on occupancy, vehicle technology, route design, and the energy source, but shared travel generally uses road and fuel resources more efficiently than many individual trips. Options A and C state harmful effects as the main result, while B contradicts the purpose of public transport. It is therefore an important green-transport practice.

Correct answer: A. Helping clean the air

The governing concept is the ecological role of trees. During photosynthesis, trees absorb carbon dioxide and release oxygen, while their leaves can intercept dust and some air pollutants. Trees also provide shade, habitat, and other ecosystem benefits. Therefore, option A is the best answer because helping improve air quality is a major benefit of tree plantation. The roots of trees generally hold soil and reduce erosion rather than increase it, so B is incorrect. Healthy vegetation does not reduce atmospheric oxygen as stated in C, and suitable tree planting can support, not reduce, local biodiversity, making D incorrect. Plantation should nevertheless use suitable native species and proper care.

Correct answer: B. Clean transport and resource saving

A sustainable city is planned to meet present needs while protecting resources and environmental quality for the future. Its governing concept is sustainable development, which balances social well-being, economic activity and ecological responsibility. Clean public transport, walking and cycling facilities can reduce fuel use, traffic pollution and greenhouse-gas emissions. Efficient buildings, renewable energy, water conservation, recycling and careful resource use are also typical features. Thus, option B is correct because it combines clean transport with saving resources. Option A represents poor waste management, option C increases air pollution, and option D wastes a limited natural resource. The correct choice is the one that reduces environmental pressure while supporting people’s needs.

Correct answer: C. Saving energy and paper

A green workplace applies environmental responsibility to everyday work practices. The governing concept is resource efficiency: achieving the required work while using less electricity, paper, water and other materials and producing less waste. Saving energy may involve switching off unused lights, using efficient equipment and selecting suitable power settings. Saving paper may involve digital documents, double-sided printing when printing is necessary, and reuse or recycling. Therefore, option C is the clear sign of a green workplace. Unnecessary printing consumes paper and ink, lights left on waste electricity, and mixing waste makes recycling and safe treatment more difficult. These distractors describe wasteful practices rather than sustainability.

Correct answer: D. Paper

A paperless office uses digital systems to create, read, share and store documents instead of routinely printing them. The governing idea is dematerialisation: replacing a physical material, where practical, with an electronic process that uses fewer physical resources. Reduced printing saves paper and can also lower the demand for ink, storage space and transport of documents. Therefore, option D, paper, is the direct and unambiguous answer. Sound is not the material being replaced, while sand and smoke are not resources normally consumed in office printing. A paperless system does not mean that digital technology has no environmental cost; devices and electricity still need responsible management, but the specific resource asked about is paper.

Correct answer: A. When unnecessary travel is reduced

A video meeting can support sustainability when it replaces travel that is unnecessary for achieving the meeting’s purpose. The governing concept is resource and emission reduction. If people participate remotely, vehicles may use less petrol or diesel, which can reduce fuel consumption, traffic congestion, air pollution and carbon dioxide emissions. Therefore, option A is correct, provided the meeting is genuinely suitable for online participation and the electricity and equipment are used responsibly. Options B and C increase travel or fuel use, while option D increases material consumption. The question asks when the meeting is green, so the relevant test is whether it avoids avoidable travel and its associated environmental impacts.

Correct answer: B. By automatically switching devices off when not in use

Smart sensors measure conditions such as movement, occupancy, temperature, light level or equipment status. The governing concept is demand-based automation: energy is supplied when a service is needed and reduced when it is not. For example, an occupancy sensor can switch off lights in an empty room, and a control system can place an idle device into a low-power mode. This lowers unnecessary electricity consumption without requiring constant manual checking. Thus, option B is correct. Keeping every device on continuously wastes energy, while polluting water and burning waste are harmful actions unrelated to sensor-based energy management. Sensors save energy through accurate detection and automatic control, not by damaging the environment.

Correct answer: C. It can analyse energy use and suggest savings

Artificial intelligence can support energy management by finding useful patterns in data from meters, sensors, buildings and equipment. The governing concept is data-driven optimisation. An AI system may compare consumption at different times, identify unusual energy use, forecast demand and recommend actions such as adjusting temperature settings, scheduling equipment or reducing operation during low-use periods. It does not automatically guarantee savings; the recommendations must be checked and implemented safely. Nevertheless, option C is correct because analysing energy use and suggesting savings is a realistic AI application. Options A, B and D describe waste or damage, not responsible energy management or an environmental benefit.

Correct answer: A. By suggesting irrigation according to need

AI can support water conservation in farming through precision agriculture. The governing concept is data-informed irrigation: decisions are based on soil moisture, weather forecasts, crop type, growth stage and sometimes satellite or field-sensor information. By combining these inputs, a system can estimate when irrigation is needed and how much water should be applied. This can reduce overwatering, runoff and pumping while still supporting crop health. Therefore, option A is correct because it connects irrigation with actual field requirements. Allowing water to flow continuously wastes water, and removing soil or burning seeds damages production rather than conserving a resource. AI provides recommendations; farmers should validate them using local conditions.

Correct answer: B. Low-pollution technology

Clean technology refers to products, processes and systems designed to provide a useful service while reducing environmental harm compared with less efficient alternatives. Its governing goals may include lower air pollution, reduced greenhouse-gas emissions, efficient use of energy and materials, less waste and protection of water and ecosystems. Examples can include renewable-energy systems, energy-efficient appliances, pollution-control equipment, water-saving devices and improved recycling processes. Therefore, option B is correct because low-pollution technology captures the central meaning. High-smoke technology increases pollution, waste-spreading technology harms land and communities, and water-damaging technology threatens a vital resource. Clean technology reduces impacts; it does not mean that every impact is automatically zero.

Correct answer: B. Saving energy and planting trees

The governing concept is individual climate action through conservation and pollution reduction. Saving electricity and fuel lowers the demand for fossil fuels and therefore helps reduce associated greenhouse-gas emissions. Planting and protecting trees supports carbon absorption and improves local environmental conditions. For these reasons, option B gives two constructive personal actions. Wasting fuel increases resource use and emissions, burning plastic can release harmful smoke and pollutants, and leaving a tap open wastes water. The correct choice is thus the one that conserves resources and supports a healthier environment rather than creating additional waste.