When humans burn fossil fuels, most of the carbon quickly enters the                       as carbon dioxide.

• Water
• Atmosphere
• Sun
• Air

What does not produce carbon dioxide?

• Photosynthesis
• Burning Fossil Fuels
• Animal respiration
• Plants decaying

How do living organisms return carbon to the atmosphere in the carbon cycle?

• respiration and photosynthesis
•  decomposition and respiration

Which of the following removes carbon from the atmosphere?

• Combustion
• Respiration
• Photosynthesis
• Death

If the plant population decreased, the amount of carbon would _________.

• Stay the same

• Increase

• Decrease

Which of the following is the best conclusion that can be made from this graph?

• atmospheric carbon dioxide levels have been decreasing since 1960
• Hawaii has a lot of carbon dioxide
• humans have been working hard to decrease carbon dioxide levels
• atmospheric carbon dioxide levels have increased steadily since 1960

The total amount of the carbon on Earth is constant.

• True

• False

Which one of these does not add CO2 to the atmosphere?

• cooking with gas
• planting trees
• burning wood
• riding in a bus

Combustion is another word for _______________.

• a train
• a bus
• a dog
• burning

What process keeps Earth's temperature suitable for life

• Convention currents
• Greenhouse Effect
• Albedo Effect
• Water Cycle