Concept:Rain clouds develop in the lowest layer of the atmosphere where weather and water vapour are present.
Explanation:The troposphere is the lowest layer of the atmosphere.
It contains almost all of the atmosphere's water vapour and dust particles.
Most weather phenomena, including cloud formation, take place in this layer.
When warm air rises, it cools and water vapour condenses to form rain clouds.
The stratosphere, thermosphere, and exosphere do not have suitable conditions for rain cloud development.
Thus, the correct option is the troposphere.
Answer:Troposphere (Option A)