Which one of the following is the densest part of the atmosphere?

The ________ is a mixture of several gases.

The lower portion of atmosphere contains

__________ contains 75% of the atmosphere's gases and large amounts of water vapour and dust.

Which layer is warm near the surface of Earth?

__________ extends several hundred kilometres upwards,from the Earth's surface.

Which is the closest layer to the Earth's surface?

Aeroplanes fly in ___________ layers.

The __________ stretches beyond the atmosphere to about 50 km,above the Earth's surface.

The layer lying above the troposphere is called