To form precipitation, cloud particles must grow up to what condition?

Correct answer: Large and heavy enough for gravity to pull them down

Correct answer: A. Newly formed cloud droplets and ice crystals are usually very small, so air currents can keep them suspended. They must grow through processes such as collision and coalescence among liquid droplets, or ice-crystal growth in cold clouds. As a particle becomes larger, its weight and downward terminal motion increase. Precipitation begins when the particle is large and heavy enough that gravity overcomes the supporting effect of updrafts and air resistance sufficiently for it to fall from the cloud. A is correct because it states the necessary physical condition. B and D are wrong because smaller or lighter particles remain suspended or move with the air. C is wrong because becoming vapour would remove the particle rather than create precipitation. The falling particle may melt, evaporate, or reach the ground as rain, snow, sleet, or hail depending on the air below. Memory cue: particle growth plus gravity produces falling precipitation.