As the river enters the plain it twists and turns forming large bends known as ______.

The correct answer is B, Selvas. Selvas is the name given to the equatorial rainforest of the Amazon basin, a multi storeyed evergreen forest of hardwoods such as mahogany, ebony and rosewood, with so many species mixed together that commercial logging of a single kind is difficult. Option A, Taiga, is wrong because the taiga is the coniferous softwood forest of the cold northern latitudes of Eurasia and North America. Option C, Steppes, is wrong because the steppes are the temperate grasslands of Eurasia, not forest at all. Option D, Campos, is wrong because the Campos is the tropical grassland of the Brazilian highlands, which lies in the same country but outside the equatorial basin. Keep the three Amazonian words apart: Selvas is the forest, Campos the grassland and the Llanos the grassland of the Orinoco.

The correct answer is B. Hot deserts lie on the western margins of continents roughly between 20 and 30 degrees north and south, under the descending dry air of the subtropical high pressure belt. The trade winds there blow from the land to the sea, so they carry no moisture inland, and cold currents such as the Canary, Benguela and Peru currents chill the air over the coast and stop it from rising, which is why fog is common but rain is not. Option A is wrong because the eastern margins in low latitudes get heavy rain from the trade winds and the monsoon. Option C is wrong because the dry lands of the high interiors, such as the Gobi, are cold deserts and lie well below 60 degrees. Option D is wrong because the polar belts are cold deserts of ice, not hot deserts.

The correct answer is B. The taiga is the belt of coniferous softwood forest between about 50 and 70 degrees latitude, and in the southern hemisphere that belt is almost entirely ocean: only the narrow tail of South America and a few islands reach it, which is far too little land for a continuous forest belt. Option A is wrong because the south is not too warm; the latitude is cool enough, there is simply no land there. Option C is wrong because conifers do grow in the south, in the mountains of Chile, New Zealand and Australia, only not as a vast belt. Option D is wrong because the southern hemisphere has great ranges such as the Andes and the Drakensberg; mountains are not the reason. This asymmetry of land and water is also why the south has a smaller annual range of temperature.

The correct answer is C, Velds and South Africa. The Velds are the temperate grasslands of the high plateau of South Africa, where maize and cattle farming and the gold mining of the Witwatersrand go together. Option A is wrong because the Pustaz is the grassland of Hungary, in the middle Danube basin. Option B is wrong because Canterbury is the grassland of the South Island of New Zealand, famous for sheep. Option D is wrong on both counts, because the Downs are the grasslands of Australia, especially the Murray Darling basin, and the grassland of Argentina is the Pampas. The question works entirely on swapped pairs, so memorise the list as one chain: Prairies in North America, Pampas in Argentina, Velds in South Africa, Downs in Australia, Steppes in Eurasia, Pustaz in Hungary and Canterbury in New Zealand.

The correct answer is B, tropical grasslands. The Llanos are the grasslands of the Orinoco basin in Venezuela and Colombia and the Campos those of the Brazilian highlands, and both lie in the savanna belt, where a hot wet season alternates with a sharply dry one and the grass grows tall and coarse with scattered thorny trees. Option A is wrong because the temperate grasslands of South America are the Pampas of Argentina, with short nutritious grass. Option C is wrong because coniferous forest is the taiga of the cold northern latitudes, far from these basins. Option D is wrong because Mediterranean scrub grows in the dry summer belts of the western margins, such as central Chile, and consists of hard leaved evergreen shrubs. Group the tropical grasslands as Savanna in Africa, Llanos in Venezuela and Campos in Brazil.