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This pie chart illustrates different gases in Earth’s atmosphere.

• Oxygen
• Carbon Dioxide
• Nitrogen
• Water Vapor

The best description of the troposphere is the layer of the atmosphere with the

• most ozone.
• greatest density.
• highest altitude.
• coldest temperature.

If cyanobacteria had failed to appear on Earth, how would the evolution of Earth’s atmosphere most likely be different?

• Earth’s atmosphere would lack significant amounts of nitrogen
• Earth’s atmosphere would consist of volcanic gases and water vapor
• Earth’s atmosphere would contain more oxygen and less carbon dioxide.
• Earth’s atmosphere would still be composed mainly of hydrogen and helium

Which best explains why air temperatures near mountaintops are often much colder than air temperatures near sea level?

• Large amounts of snowfall decrease the temperature
• Air near mountaintops is less dense.
• Strong winds near mountaintops decrease temperatures.
• The lack of vegetation at sea level allows the ground to absorb more heat.

When a plane flies, it travels through air that contains gases, liquids, and solids. This area is best described as the

• atmosphere.
• lithosphere.
• biosphere.
• hydrosphere

In which layer of Earth’s atmosphere does weather occur?

• mesosphere
• stratosphere
• thermosphere
• troposphere

A weather balloon is about 2 meters wide when it is near the ground. It grows to about 6 meters wide at higher altitudes. Which change most likely makes the balloon become wider at higher altitudes?

• More gases enter the balloon.
• The gas inside the balloon gets much hotter.
• The air pressure surrounding the balloon decreases.
• Sunlight breaks down the material of the balloon.

Which of these statements best describes temperature as elevation in the atmosphere increases?

• Which of these statements best describes temperature as elevation in the atmosphere increases?
  
• Temperature remains constant with elevation in the mesosphere.
• Temperature remains constant with elevation in the mesosphere.
• Temperature generally decreases with elevation in the troposphere.

A scientist compared the atmospheric composition of a newly discovered planet to the atmosphere of Earth.

Which conclusion about the unknown planet can be made by using the information provided?

• It is not suitable for animals.
• It will sustain a small human population.
• It has enough oxygen for small mammals.
• It has many carbon dioxide-releasing organisms.

The temperature of the stratosphere increases with altitude because of the presence of

• nitrogen.
• water vapor.
• ozone
• carbon monoxide.