When can ice particles mostly form in clouds?

Correct answer: In very cold conditions at height

Direct answer: B, in very cold conditions at height. Temperature generally decreases with altitude in the lower atmosphere, so the upper parts of many clouds can become cold enough for water to freeze or for ice crystals to form. Water vapour may deposit directly as ice, or supercooled droplets may freeze when suitable particles are present. These ice particles can grow and later fall as snow, or melt while passing through warmer air and reach the ground as rain. A is wrong because strong heat at low height favours liquid water and evaporation, not the usual formation of cloud ice. C describes a possible source of moisture through evaporation, but a warm sea surface itself is not where cloud ice mainly forms. D is unrelated to ice formation inside clouds. The exact temperature and cloud conditions matter, but the key school-level link is high altitude plus very low temperature. Memory cue: high cloud levels are colder, so ice becomes possible.