Global warming refers to ____.

• The gradual decrease in Earth's temperature

• The rapid increase in Earth's temperature due to volcanic eruptions

• The gradual increase in temperature of Earth

• The sudden drop in temperature caused by deforestation

Trees absorb ____ from the atmosphere.

• Carbon monoxide

• Oxygen

• Carbon dioxide

• Nitrogen

Human activities that contribute to greenhouse gases include ____.

• Fishing, agriculture, solar energy

• Mining, burning fossil fuels, raising livestock, deforestation

• Recycling, wind energy, organic farming

• Hunting, nuclear energy, afforestation

Fossil fuels are ____.

• Rocks

• Minerals

• The substance formed from the remains of organisms

• Metals

Much of the greenhouse gases come from humans burning ____.

• Wood

• Paper

• Plastic

• Fossil fuels

Fossil fuels release ____ amount of energy, carbon dioxide and other greenhouse gases when burned.

• A small

• A large

• A moderate

• A negligible

Greenhouse gases include ____.

• Oxygen, nitrogen, carbon dioxide, water

• Carbon dioxide, methane, nitrous oxide, water vapors

• Hydrogen, helium, carbon dioxide, neon

• Methane, oxygen, argon, nitrogen

If there is ____ carbon dioxide in the atmosphere, Earth will not retain much solar energy and cool down.

• More

• Less

• Equal

• Variable

If there is ____ carbon dioxide in the atmosphere, Earth will retain more solar energy and heat up.

• More

• Less

• Equal

• Variable

Global temperature has been rising from the past ____ years.

• 100

• 140

• 200

• 240