Preparing trial balance and correcting errors

Correct answer: D. Where the river bed is rocky and uneven, often with a steep gradient

D is correct. Rapids form where a river flows quickly over an uneven bed, often on a steep gradient. Rock ledges and boulders disrupt the flow, making it turbulent. Flat, quiet delta water is generally slower.

Correct answer: C. A bow-shaped front with spreading distributaries

An arcuate delta has a roughly bow-shaped or fan-shaped seaward margin, with distributary channels spreading across the deposited sediment. It develops where river deposition is balanced to some extent by wave and current reworking. Option C is correct because it names the diagnostic outline and channel pattern. Caves, wind dunes, and subglacial ridges belong to karst, aeolian, and glacial environments.

Correct answer: C. Fewer condensation nuclei will be available

The correct answer is C. Cloud droplets often form when water vapour condenses on tiny particles called condensation nuclei. Dust, sea-salt particles and other aerosols provide surfaces on which water can gather. The process can be understood step by step: moist air cools, water vapour becomes ready to condense, and tiny particles provide suitable surfaces for droplets to begin forming. If dust and salt particles are scarce, fewer condensation nuclei are available, so cloud-droplet formation may become more difficult, even though cooling and high humidity can still allow condensation in some conditions. A is wrong because nitrogen does not suddenly begin burning. B is wrong because a shortage of particles does not remove oxygen. D is wrong because argon does not turn into water vapour. Memory cue: nuclei are the tiny starting surfaces for cloud droplets.