Which of the following synthetic chemical is responsible for ozone layer depletion?

The correct answer is A, Sardar Sarovar. The Narmada Bachao Andolan grew up against the Sardar Sarovar dam on the Narmada.

The movement began in 1985 under Medha Patkar, with Baba Amte and others joining later. It argued that raising the dam's height would submerge villages and forests in Madhya Pradesh, Maharashtra and Gujarat and that the people displaced were not being resettled properly. The protest used fasts, rallies and the courts, and in 1993 it made the World Bank withdraw from the project. The Supreme Court allowed construction to continue in 2000 with conditions on rehabilitation.

Option B, Bhakra Nangal, is on the Sutlej in Himachal Pradesh and Punjab. Option C, Rihand, is in Uttar Pradesh on a tributary of the Son. Option D, Tehri, on the Bhagirathi in Uttarakhand, had its own protest led by Sunderlal Bahuguna, not the Narmada Bachao Andolan.

Exam tip: Narmada Bachao - Medha Patkar, Sardar Sarovar; Chipko and Tehri - Sunderlal Bahuguna.

The correct answer is C, Glacier. A glacier is a natural mass of moving ice and a source of fresh water, not a pollutant.

A water pollutant is any substance added to water that makes it unfit for use. Pollutants are grouped as physical, such as silt, heat and colour; chemical, such as heavy metals, fertilisers, pesticides and detergents; and biological, such as bacteria and viruses from sewage. Glaciers in the Himalayas feed the Ganga, Yamuna and Brahmaputra, so they supply water rather than spoil it.

A is wrong as a choice because chromium is a heavy metal discharged by tanneries and electroplating units and causes serious harm. B is wrong because silt, washed in by erosion, raises turbidity, cuts light for aquatic plants and is treated as a physical pollutant. D is wrong because arsenic in groundwater, a known problem in West Bengal and Bihar, causes arsenicosis and skin cancer.

Exam tip: Physical pollutants - silt and heat; chemical - chromium, arsenic, fluoride; biological - pathogens from sewage.

The correct answer is A, Bihar. Kabartal Wetland, known locally as Kanwar Jheel, lies in Begusarai district of Bihar and was designated a Ramsar site in 2020, becoming the first Ramsar site in the state. It is an oxbow lake left behind by the shifting course of the Burhi Gandak in the Indo-Gangetic plain, spreads over about 2,600 hectares, and works as a natural flood buffer for the area. It is an important halt on the Central Asian Flyway, where migratory birds such as the greylag goose and the endangered sociable lapwing have been recorded. Option B is wrong because Himachal Pradesh's Ramsar sites are Renuka, Pong Dam Lake and Chandertal. Option C is wrong because Punjab's include Harike, Kanjli, Ropar, Nangal, Beas Conservation Reserve and Keshopur-Miani. Option D is wrong because Haryana's Sultanpur and Bhindawas were both named in 2021. Exam tip: Kanwar Jheel or Kabartal in Begusarai is Bihar's first Ramsar site, an oxbow lake of the Burhi Gandak.

The correct answer is D, Lonar. Lonar Lake, in Buldhana district of Maharashtra, was added to the list of Ramsar sites in November 2020 along with Sur Sarovar in Uttar Pradesh. The lake fills a crater punched into the Deccan basalt by a meteorite about fifty thousand years ago, which makes it the only such crater in basaltic rock in India, and its water is unusual for being saline and alkaline at the same time, supporting rare micro-organisms. The Ramsar Convention on wetlands was signed in 1971 in the Iranian city of Ramsar, and India became a party in 1982. Option A is wrong because Vihar is a reservoir that supplies water to Mumbai. Option B is wrong because Venna is a man-made lake at Mahabaleshwar. Option C is wrong because Rankala is a lake inside Kolhapur city, and none of these carries Ramsar status. Exam tip: Nandur Madhmeshwar was Maharashtra's first Ramsar site, followed by Lonar and Thane Creek.

The correct answer is C, mercury. The Minamata Convention on Mercury was adopted in 2013 and entered into force in 2017. It controls the supply and trade of mercury, restricts its use in products such as batteries, switches and certain measuring devices, and regulates emissions from coal burning and from small-scale gold mining. It is named after the Japanese city of Minamata, where industrial discharge of mercury compounds into the bay caused severe neurological disease from the nineteen fifties.

Option A, lead, is regulated by national laws on petrol, paint and pipes rather than by a dedicated global convention. Option B, asbestos, appears in the annexes of the Rotterdam Convention on prior informed consent. Option D, arsenic, is a serious contaminant of groundwater in parts of South Asia but is dealt with through drinking water standards and national programmes, not by a treaty of its own.