Choose the odd pair among the following options.

Question

UnlockIAS · Accepted Answer

Correct — C, Kalahari : America. The relation running through the list is desert-to-place, and three of the four pairs hold while one does not. The Kalahari is not American: it is a large semi-arid sandy savanna in southern Africa covering about 900,000 sq km, taking in much of Botswana together with parts of Namibia and South Africa. Placing it in America is a straightforward error of continent, and it is the only error on the list. Check the other three in turn. The Thar, the Great Indian Desert, covers 264,091 sq km of which 195,091 sq km lie inside India, principally in western Rajasthan, with the remainder in Pakistan — so 'Thar : India' is right, and its being shared with a neighbour does not make it wrong. The Sahara, at about 9.2 million sq km the largest hot desert on earth, spans northern Africa from the Atlantic to the Red Sea, so 'Sahara : Africa' is right. The Gobi, about 1,295,000 sq km of cold desert, lies across southern Mongolia and northern China, so 'Gobi : Mongolia' is right on the same shared-territory reasoning that validates the Thar. The deserts that would have made option (c) true are American ones the setter deliberately left out — the Atacama in Chile, the Sonoran, Mojave and Chihuahuan of North America, the Great Basin, and the Patagonian desert of Argentina. None of them is the Kalahari.

Why the other options are wrong — (a) Correctly matched, so it cannot be the odd one. The Thar covers 264,091 sq km in all, with 195,091 sq km — roughly three-quarters — inside India, spread over western Rajasthan and reaching into Gujarat, Haryana and Punjab, and the rest in Pakistan's Sindh and Punjab. A candidate may hesitate because it is a transboundary desert, but the pair asks where the Thar is, not where it is exclusively.  (b) Correctly matched and the least disputable pair on the list. The Sahara covers about 9.2 million sq km of northern Africa, making it the largest hot desert in the world and roughly the size of the United States or of China. It is here as a control — an obviously true pair against which the reader is meant to calibrate the others.  (d) Correctly matched. The Gobi covers about 1,295,000 sq km across southern Mongolia and the northern part of China's Inner Mongolia, and it is a cold desert — its aridity comes from the rain shadow of the Himalaya and from sheer distance inland, not from tropical high pressure. The pairing with Mongolia is exactly how it is named and taught.

Concept: Deserts are defined by aridity rather than by heat, and the world's major ones fall into three groups by the mechanism that dries them. Tropical or subtropical deserts sit near 20 to 30 degrees latitude in the belt of descending air of the subtropical high, and typically hug the western margins of continents inside the trade-wind belt, where cold offshore currents strengthen the aridity — the Sahara, the Kalahari and Namib, the Australian deserts, the Atacama. Continental or mid-latitude deserts are dry because they lie far from any ocean and behind mountain barriers — the Gobi and the Taklamakan sit in that class, which is why they are cold deserts with freezing winters. Rain-shadow deserts are dried by a mountain wall — Ladakh's cold desert behind the Great Himalaya is India's example. The Thar is a partial exception that is worth understanding rather than memorising: it lies in the monsoon's path, but the moisture-bearing Arabian Sea current runs parallel to the Aravallis instead of being lifted by them, so the rain falls elsewhere.

State PCS 2025 Q65 — Science & Technology PYQ with Answer

State PCS 2025 Q65 — Science & Technology PYQ with Answer