Q.(a) What do you mean by sustainable development ?

The definition you have quoted — “development that meets the needs of the present without compromising the ability of future generations to meet their own needs” — is the most widely accepted and foundational statement of sustainable development. It first appeared in a landmark report titled Our Common Future, published in 1987 by the World Commission on Environment and Development. That commission is often called the Brundtland Commission, after its chair, Gro Harlem Brundtland.

Now, the question asks which United Nations body gave this definition. The Brundtland Commission was not itself a permanent UN committee or conference; it was a special, temporary commission set up by the United Nations. However, the definition was formally adopted and popularised by the United Nations Conference on Environment and Development (UNCED), held in Rio de Janeiro in 1992 — famously known as the Earth Summit. It was at this conference that the world’s nations officially embraced the Brundtland definition as the guiding principle for global environmental and developmental policy.

Let us look at the options one by one:

• (A) United Nations Conference on Environment and Development — This is correct. UNCED is the full name of the 1992 Earth Summit, which endorsed the Brundtland definition.
• (B) United Nations Committee on Environment and Development — No such permanent committee exists with that exact name. The Brundtland Commission was a commission, not a committee, and its work was adopted by the conference. …

Sustainable development is an approach to progress that meets the needs of the present without compromising the ability of future generations to meet their own needs. It involves balancing economic growth with environmental protection and social equity. A crucial aspect of achieving sustainable development is the adoption of energy sources that are renewable, reduce pollution, and are locally available, especially in rural contexts.

The image provided depicts a biogas plant, commonly known as a gobar gas plant in India. This technology converts organic waste, primarily animal dung (gobar) and agricultural residues, into biogas (a mixture of methane and carbon dioxide) and nutrient-rich slurry. Biogas can be used as cooking fuel, for lighting, or to generate electricity, replacing traditional fuels like firewood, kerosene, or LPG. The slurry, a byproduct, is an excellent organic fertilizer, reducing the need for chemical fertilizers.

Let's evaluate the given options in light of the image and the concept of sustainable development:

• A) Non-conventional source of energy: This is a broad category that includes solar, wind, hydro, geothermal, and biomass energy (which biogas falls under). While gobar gas is indeed a non-conventional source of energy, this option is a general classification rather than the specific strategy depicted in the image. The question asks to identify that strategy given in the image.
• B) Wind power: Wind power involves harnessing wind energy through turbines to generate electricity. It is a clean, renewable energy source and contributes to sustainable development. However, the image clearly shows a biogas plant, not a wind turbine.
• C) CNG in urban areas: Compressed Natural Gas (CNG) is a fossil fuel, primarily methane, used as an alternative to petrol and diesel in vehicles, particularly in urban areas to reduce air pollution. While it is cleaner than petrol/diesel, it is still a non-renewable fossil fuel. More importantly, the image does not depict any aspect of CNG usage or infrastructure.
• D) Gobar Gas in rural areas: This option directly and accurately describes the technology shown in the image. Gobar gas plants are predominantly installed in rural areas where livestock is abundant, providing a continuous supply of raw material (dung).

The use of gobar gas in rural areas is an exemplary strategy for sustainable development because: …

Mini-hydel plants are small-scale, run-of-the-river hydroelectric installations that harness the flow of perennial hill streams to generate electricity without large dams or reservoirs. The NCERT chapter on Environment and Sustainable Development lists them as a strategy for sustainable development and highlights three features that make them eco-friendly. Let us examine each statement.

Statement (i): they generate electricity only for local areas. Because the power generated is consumed locally, electricity need not be carried over long transmission lines. This avoids the transmission-and-distribution losses and the extensive grid infrastructure (towers, cleared corridors) that long-distance supply requires, so local generation is treated here as an environmental advantage. Correct.

Statement (ii): they do not change the land use pattern. Unlike large hydro projects that submerge forests, farmland and settlements behind a reservoir, mini-hydel plants need no large storage reservoir. The surrounding land — forest, agricultural or otherwise — is left undisturbed, so they do not alter the existing land-use pattern. Correct. …

Part (a)

The Montreal Protocol (1987) was framed specifically to phase out substances that deplete the stratospheric ozone layer — chiefly chlorofluorocarbons (CFCs) used in refrigerants, aerosols and foam-blowing. It set binding reduction targets for developed and developing nations and is among the most successful environmental treaties, with the ozone layer now recovering. The distractors address other problems: the Kyoto Protocol (1997) and the Paris Agreement (2015) target greenhouse-gas emissions and climate change, while the Brundtland Commission Report (1987) popularised “sustainable development” but is a report, not a substance-banning treaty. …