About three-fourths of world's cobalt, a metal required for the manufacture of batteries for electric motor vehicles, is produced by

The correct answer is B, Only two. Rows 3 and 4 are correct; rows 1 and 2 have the wrong region or type.

Fold mountains form when plates converge and layers of rock crumple. The Appalachians of eastern North America are old fold mountains raised in the Palaeozoic era and since worn down, and the Andes of South America are young fold mountains formed where the Nazca plate dives beneath the South American plate, so rows 3 and 4 are right. Block mountains form when a block of land is raised between faults; the Vosges in France and the Black Forest in Germany are classic examples, standing on either side of the Rhine rift valley. So row 1 is wrong, as the Vosges are in Europe and are block mountains. Row 2 is wrong because the Alps are young fold mountains, like the Himalayas.

A is wrong: two rows, not one, are correct.

C is wrong: only rows 3 and 4 are correct.

D is wrong: rows 1 and 2 contain errors.

Exam tip: block mountains = Vosges and Black Forest (Rhine rift); young fold = Alps, Himalayas, Andes, Rockies; old fold = Appalachians, Aravallis, Urals.

The correct answer is A, Only one. Only row 2 is fully correct; rows 1 and 3 each have a wrong entry.

Hundru Falls, near Ranchi in Jharkhand, is formed where the Subarnarekha river drops off the edge of the Ranchi plateau, part of the Chota Nagpur region, so row 2 is right. Dhuandhar Falls is on the Narmada at Bhedaghat near Jabalpur, where the river plunges into the marble gorge; Jabalpur lies in the Mahakoshal region between the Vindhya and Satpura ranges, not on the Malwa plateau, so row 1 fails on the region. Gersoppa Falls, better known as Jog Falls, is in the Western Ghats of Shivamogga district, Karnataka, but it is formed by the Sharavathi river, not the Netravati, so row 3 fails on the river.

B is wrong: only one row, not two, is correct.

C is wrong: rows 1 and 3 contain errors.

D is wrong: row 2 is correctly matched.

Exam tip: Jog/Gersoppa = Sharavathi; Dhuandhar = Narmada at Bhedaghat, Jabalpur; Hundru = Subarnarekha, Ranchi.

The correct answer is D, Rann of Kutch. The Rann was once a shallow arm of the Arabian Sea, and as the sea withdrew from it, aided by the uplift of the land, it was left as the vast salt marsh seen today.

The Great and Little Rann of Kutch in Gujarat cover tens of thousands of square kilometres of flat, salty mudflats that are flooded during the monsoon and turn into a white salt desert in the dry season. Geologists explain the landscape by repeated changes in sea level together with tectonic uplift: the former gulf became cut off from the sea and was filled by sediments brought by rivers such as the Luni. Its size and origin make it the classic Indian example of a marsh left behind by a retreating sea.

A is wrong: Bhitarkanika in Odisha is a mangrove forest in the delta of the Brahmani and Baitarani rivers, formed by river and tidal action.

B is wrong: Marakkanam in Tamil Nadu is a coastal salt-making area, not an extensive marshland.

C is wrong: Naupada in Andhra Pradesh is a small coastal swamp and salt-pan area.

Exam tip: Rann of Kutch = former arm of the Arabian Sea, now a seasonal salt marsh; home of the Indian wild ass in the Little Rann.

The correct answer is B, Gomati - Ghaghara - Gandak - Kosi. Below Prayagraj the Ganga receives the Gomati first, then the Ghaghara, then the Gandak and finally the Kosi as it flows east.

The Gomati, which rises near Pilibhit and flows past Lucknow and Jaunpur, joins the Ganga near Kaithi in Ghazipur district of Uttar Pradesh. The Ghaghara, coming down from Nepal as the Karnali, meets the Ganga near Chhapra in Bihar. The Gandak, known as the Narayani in Nepal, joins at Sonpur opposite Patna. The Kosi, the "Sorrow of Bihar" famous for shifting its course, joins near Kursela in Katihar district, close to the border with Jharkhand and West Bengal.

A is wrong: it puts the Ghaghara before the Gomati, but the Gomati joins further west.

C is wrong: it puts the Ghaghara first and the Kosi before the Gandak.

D is wrong: the Gandak joins near Patna, well west of the Kosi confluence at Kursela.

Exam tip: left-bank order below Prayagraj = Gomati (Ghazipur), Ghaghara (Chhapra), Gandak (Sonpur-Patna), Kosi (Kursela).

The correct answer is C, Côte d'Ivoire and Ghana. These two neighbouring West African countries grow well over half of the world's cocoa.

Cocoa is a tropical tree crop that needs heavy, well-spread rainfall, high humidity, temperatures of about 21 to 32 °C and shade, which is why it grows best within about 10 degrees of the Equator. The humid forest belt along the Gulf of Guinea offers exactly these conditions, and Côte d'Ivoire (Ivory Coast) ranks first and Ghana second in world output. In India cocoa is grown mainly in Kerala, Karnataka, Andhra Pradesh and Tamil Nadu, often as an intercrop with arecanut and coconut.

A is wrong: Algeria and Morocco lie in dry North Africa, where cocoa cannot grow.

B is wrong: Botswana and Namibia are arid southern African countries known for diamonds and minerals.

D is wrong: Madagascar is famous for vanilla and Mozambique for cashew, not for leading cocoa output.

Exam tip: cocoa = Gulf of Guinea; Côte d'Ivoire first, Ghana second.