Which one of the following pairs is not correctly matched?

The correct answer is D, near the equator. The Inter Tropical Convergence Zone is the low-pressure belt near the equator where the north-east and the south-east trade winds meet. Strong heating by the overhead sun makes the air rise, so surface pressure stays low, winds are light and the sky is cloudy with heavy convectional rain; sailors called this calm belt the doldrums. The zone does not stay fixed: it shifts north in June and July and south in December and January with the apparent movement of the sun, and its northward shift helps the south-west monsoon advance over India. A is wrong because the belt between the trade winds and the westerlies is the subtropical high-pressure belt at about 30 degrees. B is wrong because the belt between the westerlies and the polar winds is the sub-polar low at about 60 degrees. C is wrong because the poles carry permanent high pressure. Exam tip: equatorial low means ITCZ, doldrums and convectional rainfall.

The correct answer is B, Himachal Pradesh. Himachal Pradesh lies west of the Nepal border, so it touches China in the north but never Nepal. Five Indian states share a boundary with Nepal - Uttarakhand, Uttar Pradesh, Bihar, West Bengal and Sikkim - and the border runs for about 1,751 kilometres. Bihar has the longest stretch of it and the Indo-Nepal border is an open one, crossed without a passport or visa under the Treaty of Peace and Friendship of 1950. A is wrong because Uttarakhand meets Nepal along the Kali or Sharda river, with the disputed Kalapani area at its head. C is wrong because Bihar's whole northern plain, from West Champaran to Kishanganj, lies along Nepal. D is wrong because Uttar Pradesh touches Nepal through districts such as Lakhimpur Kheri, Bahraich, Shrawasti, Siddharthnagar and Maharajganj. Exam tip: the five Nepal states from west to east are Uttarakhand, Uttar Pradesh, Bihar, West Bengal and Sikkim.

The correct answer is C, the theory of plate tectonics. Plate tectonics says the Earth's rigid outer shell is broken into plates that keep moving slowly, carried by convection currents in the mantle below. The theory took shape in the 1960s, after Harry Hess explained sea-floor spreading, and the term was given by Tuzo Wilson and others. There are seven major plates and many minor ones, moving a few centimetres a year, and almost all earthquakes, volcanoes, fold mountains and deep trenches occur where they meet. A is wrong because Alfred Wegener's continental drift of 1912 moved only the continents and could not name a force strong enough to do it. B is wrong because Pangaea is the name of the single super-continent, not a theory of motion. D is wrong because plate boundaries are the edges where plates meet, a part of the theory and not the theory itself. Exam tip: Wegener gave continental drift in 1912, Hess gave sea-floor spreading in 1960, and plate tectonics followed.

The correct answer is A, Aluminium manufacturing. Muri, a town in the Ranchi district of Jharkhand, has a large alumina refinery, so it is remembered as an aluminium centre. The works began in 1948 and are now run by Hindalco; they treat bauxite mined on the Lohardaga, Gumla and Palamu plateaus and turn it into alumina, the powder from which aluminium metal is smelted. Bauxite close by, coal-based power from the Damodar valley and a rail link are what put the industry there. B is wrong because copper in this region is smelted at Ghatsila in the Singhbhum copper belt. C is wrong because the steel plants of the area are at Jamshedpur and Bokaro, not Muri. D is wrong because the fertiliser unit of this belt stands at Sindri near Dhanbad. Exam tip: pair the Jharkhand towns - Muri with aluminium, Ghatsila with copper, Jamshedpur and Bokaro with steel, Sindri with fertiliser.

The correct answer is B, 1981. India's annual rate of population growth reached its peak in the two decades from 1961 to 1981 and has fallen in every census decade since 1981, which is why demographers date the turn to that year. The total number of people still rises, because a young age structure keeps the number of births high, but the rate at which it rises has come down; this stage, with death rates already low and birth rates now following them down, is the third stage of the demographic transition. The decade from 1911 to 1921 was the only one of the last century in which the population actually fell, mainly because of the influenza epidemic, so 1921 is called the demographic divide. A is wrong because the decline had begun a full decade before 1991. C is wrong because growth was still rising after 1951. D is wrong because the decade from 1971 to 1981 recorded the highest growth rate of all. Exam tip: 1921 is the demographic divide, growth peaks by 1981 and falls after it.