Cloud droplets collide to form larger droplets in a process called coalescence
Answer: Option A
Step-by-step explanation:
When the drop lets of the cloud which are present in the air bang into each other, the result is the formation of a bigger drop let of the cloud and this whole process is known as coalescence.
And such big drop lets are big enough in their size which can result in the rainfall in that region. The droplet should at least reach a size of 4 mm to result into rainfall and this collision is a fast process.