The centre of a cyclone is a calm area. It is called the ______ of the storm.

The correct answer is B, chemical weathering. Abundant rainfall, warm temperatures and thick vegetation together supply the water, the heat and the organic acids that speed up solution, hydrolysis, hydration, carbonation and oxidation, so minerals are decomposed deeply. That is why the humid tropics carry thick red laterite crusts of iron and aluminium oxides and deep residual soils. Option A, frost weathering, needs repeated freezing and thawing of water in cracks and therefore belongs to high mountains and cold temperate lands. Option C, salt crystallisation, needs evaporation of salty moisture and is typical of arid and coastal regions. Option D, block disintegration, is a mechanical result of wide daily temperature ranges and so dominates hot deserts and cold rocky uplands. The pairing to memorise is simple: hot deserts give mechanical weathering, humid tropics give chemical weathering, and high latitudes and altitudes give frost action.

The correct answer is B, a deep glacial trough later invaded by the sea. A valley glacier reaching the coast scoops its floor below present sea level; when the ice melts and the sea rises, water floods the trough and leaves a long, narrow, steep-sided inlet with great depth. Norway, Chile, New Zealand and Greenland have the best examples. Option A is wrong because wind in deserts hollows shallow basins and shapes yardangs, and cannot cut a deep drowned valley. Option C describes a crater or caldera lake, such as Lonar in Maharashtra, which is circular and unconnected to the sea. Option D describes a gorge or canyon of river erosion, which keeps a V-shaped cross section rather than the U-shaped profile of glacial work. The cross section is the clue examiners rely on: a river cuts a V, a glacier widens it into a U, and a drowned U is a fjord.

The correct answer is A, Slovenia. The term comes from the Kras or Karst plateau of the Dinaric region, which lies largely in present-day Slovenia and extends into the neighbouring coastal belt. The limestone there is riddled with sinkholes, dolines, swallow holes, caverns and underground streams, and geographers adopted the local name for every landscape where soluble rock is sculpted by groundwater. In India the Borra caves of Andhra Pradesh and the caves of the Meghalaya plateau show the same features. Option B, Greece, has extensive limestone but did not give the landform its name. Option C, Switzerland, is associated with alpine and glacial terms such as cirque and arete rather than with karst. Option D, Norway, is remembered for fjords, the drowned glacial troughs of its western coast. Examiners like to combine this question with the pairing of carbonation as the process and limestone or dolomite as the rock.

The correct answer is C, moraine. A moraine is the ridge of unsorted rock debris that a glacier carries and dumps; it is named by position as lateral, medial, ground or terminal moraine, and the terminal moraine marks the farthest point the ice reached. Option A, a cirque, is an armchair-shaped hollow cut at the head of a glacial valley by plucking and abrasion, so it is erosional. Option B, an arete, is the sharp knife-edged ridge left where two cirques erode back towards each other, again erosional. Option D, a horn, is the pyramidal peak produced when three or more cirques eat into the same mountain mass, the Matterhorn being the classic example, and it too is erosional. The other depositional forms of ice that papers ask about are drumlins, eskers, kames and outwash plains, so a safe way to answer is to recall that erosion by ice hollows and sharpens, while deposition by ice piles up.

The correct answer is B, northern China. Loess is a depositional landform of wind: very fine silt lifted from desert and glacial margins is carried far away and settles as a yellow, porous, loosely packed sheet. The thickest and most extensive sheets on earth are in the loess plateau of northern China, which gives the Huang He its colour and its name, the Yellow River. Option A, Brazil, lies mostly in humid tropics where chemical weathering and thick forest cover prevent such deposition. Option C, Canada, carries glacial deposits such as moraines, drumlins and eskers, with only small patches of loess. Option D, Australia, has large deserts but its wind deposits take the form of long seif dunes rather than great loess sheets. A connected fact worth remembering is that loess soils are naturally fertile and self-draining, which is why the Chinese loess belt supports dense farming despite its extreme vulnerability to gully erosion.