The correct option is A Troposphere
The lowest region of atmosphere in which the human beings
along with other organisms live is called troposphere. It extends up to the height of approximately 10 km from sea level. Above the troposphere, between 10 and 50 km above sea level lies
stratosphere. Troposphere is a turbulent, dusty zone containing air, much water vapour and clouds. This is the region of strong air movement and cloud formation. The stratosphere, on the other hand, contains dinitrogen (N2), dioxygen (O2), ozone and little water vapour