Which of these rivers primarily flows in South Africa?

The correct answer is C, Jaisalmer. A khadin is a long earthen embankment built across the lower end of a sloping field, so that rainwater running off the higher rocky ground collects behind it. The water soaks into the soil during the monsoon, and in winter crops such as wheat and gram are grown on the moist bed without any further irrigation, while wells below the bund also get recharged. The system is credited to the Paliwal Brahmins of Jaisalmer, who developed it around the 15th century, and it suits the district's stony, sloping land and very low rainfall. It is one of the best examples of runoff farming in the Thar. Option A is wrong because Nagaur is not the home of the khadin system. Option B is wrong because Bikaner is known for other rainwater structures, such as the kund and the kui. Option D is wrong because Pali, on the eastern side of the Luni basin, is not where khadins developed. Exam tip: khadin, Paliwal Brahmins, Jaisalmer; kund and tanka store rainwater; kui taps seepage water.

The correct answer is D, A-iv, B-i, C-ii, D-iii. The Rapti rises in Nepal, flows past Gorakhpur in Uttar Pradesh and joins the Ghaghra, which then meets the Ganga. The Tista, or Teesta, rises from glaciers in Sikkim, cuts through the Darjeeling hills and joins the Brahmaputra, known there as the Jamuna, in Bangladesh. The Hiran is a small tributary of the Narmada that joins it from the north in Madhya Pradesh. The Purna rises in the Ajanta hills of Maharashtra and joins the Godavari; do not confuse it with another Purna that joins the Tapi. Option A is wrong because it sends the Tista to the Narmada and the Purna to the Brahmaputra. Option B is wrong because it links the Rapti with the Brahmaputra and the Hiran with the Godavari. Option C is wrong because it makes the Rapti a tributary of the Godavari. Exam tip: Rapti–Ghaghra, Tista–Brahmaputra, Hiran–Narmada, Purna–Godavari, and a second Purna joins the Tapi.

The correct answer is A, A-ii, B-iii, C-iv, D-i. The Gobi is a cold desert of Asia spread over Mongolia and northern China, and it is famous for its dinosaur fossils. Patagonia lies in southern Argentina in South America; it is a rain-shadow desert, dry because the Andes block the moist westerly winds coming from the Pacific. The Great Victoria Desert is the largest desert of Australia, stretching across Western Australia and South Australia. The Kalahari covers most of Botswana and parts of Namibia and South Africa, in southern Africa. Paper setters like Patagonia because it lies on the eastern side of its continent, while most hot deserts lie on the western margins, next to cold ocean currents. Option B is wrong because it puts the Gobi in Australia and Patagonia in Asia. Option C is wrong because it places Patagonia in southern Africa and the Victoria Desert in South America. Option D is wrong because it gives every desert the wrong continent. Exam tip: Gobi–Asia, Patagonia–South America, Great Victoria–Australia, Kalahari–southern Africa.

The correct answer is C, Silchar to Porbandar. The East-West Corridor is one arm of the National Highways Development Project, planned together with the North-South Corridor from Srinagar to Kanyakumari. It runs for about 3,300 km from Porbandar on the Saurashtra coast of Gujarat, through Rajasthan, Madhya Pradesh, Uttar Pradesh, Bihar and West Bengal, and across the narrow Siliguri corridor into Assam, ending at Silchar in the Barak valley. The two corridors cross at Jhansi in Uttar Pradesh, a point that exams love to ask. In Rajasthan the route passes Udaipur, Chittorgarh and Kota, so it matters for Rajasthan papers too. Option A is wrong because neither Imphal nor Ahmedabad is an end point of the corridor. Option B is wrong because Dimapur and Vadodara are not its terminal cities. Option D is wrong because the corridor does not end at Kandla, a port on the Gulf of Kutch; its western end is Porbandar. Exam tip: North-South = Srinagar to Kanyakumari; East-West = Silchar to Porbandar; they meet at Jhansi.

The correct answer is A, North Sea. Both rivers flow north-west across the plains of Europe and end in the North Sea. The Rhine rises in the Swiss Alps, forms part of the borders of Switzerland, Germany and France, flows through Germany and enters the sea through the Netherlands, where Rotterdam, Europe's busiest port, stands at its mouth. The Elbe rises in the Czech Republic, flows through Germany past Dresden and reaches the North Sea below Hamburg, another major port. Because of these river ports, the North Sea coast is one of the busiest shipping zones in the world. Option B is wrong because the Mediterranean receives rivers such as the Rhone, the Ebro and the Nile. Option C is wrong because the Adriatic, an arm of the Mediterranean between Italy and the Balkans, receives the Po. Option D is wrong because the Black Sea receives the Danube, the Dnieper and the Dniester. Exam tip: Rhine and Elbe to the North Sea; Danube to the Black Sea; Rhone to the Mediterranean; Po to the Adriatic.