The atmosphere is

• the layer in which weather occurs
• the layer that contains the ozone layer
• the layer of water in the oceans
• the layer of gases that surrounds Earth

The two most abundant gases in the atmosphere are

• carbon dioxide and oxygen
• carbon dioxide and nitrogen
• nitrogen and oxygen
• nitrogen and hydrogen

Ozone is

• a form of oxygen with three oxygen atoms combined
• a form of nitrogen with three nitrogen atoms combined
• a form of oxygen with two oxygen atoms in each molecule
• a form of nitrogen with two nitrogen atoms in each molecule

Earth's atmosphere is important to living things because it

• contains dust and other particles
• is very thin compared to the size of Earth
• provides all the gases that living things need to survive
• maintains a constant relative humidity

The layers of the atmosphere are classified according to changes in

• altitude
• density
• pressure
• temperature

The layer in our atmosphere in which weather occurs is the

• troposphere
• stratosphere
• mesosphere
• exosphere

The ozone layer protects living things on Earth from

• visible light
• UV radiation
• carbon dioxide

When you breathe in, you breathe in mostly which gas?

• oxygen
• carbon dioxide
• nitrogen
• argon

Which layer extends from the top of the troposphere to the bottom of the mesosphere?

• stratosphere
• meteors
• troposphere
• thermosphere

Which layer protects Earth from being hit by most meteors?

• troposphere
• stratosphere
• mesosphere
• thermosphere