Which atmospheric layer contains 75% of the mass of Earth's air? 

A)  the thermosphere 
B)  the troposphere 
C)  the mesosphere 
D)  the stratosphere

Atmospheric Layer

A layer in the Earth's atmosphere characterized by specific temperature and pressure conditions, such as the stratosphere or troposphere.

Earth's Air

The mixture of gases surrounding the planet, known as the atmosphere, which is crucial for supporting life by providing oxygen and protecting against solar radiation.

Troposphere

The lowest layer of Earth's atmosphere, where weather phenomena like rain, snow, and storms occur.