Since the first Earth Day started on April 22, 1970, people around the world have been encouraged to protect the environment and natural resources.Gaylord Nelson started this holiday.On the first Earth Day, 20 million people took part in Earth Day events. Earth Day activities can include learning something about technology like cars that are more environmentally friendly and special houses that save energy and water.An organization called the Earth Day Network encourages people to use clean energy which doesn't pollute the environment.Most of our energy comes from fossil fuels that are found underground. Coal, oil and natural gas are examples of fossil fuels.Fossil fuels come from plants and animals that lived millions of years ago. Burning fossil fuels to create energy pollutes the air and water. Many scientists think that burning fossil fuels also increases the temperature of the earth. To reduce the use of fossil fuels. scientists are experimenting with hydrogen-powered cars. These cars don't pollute the air like gas-powered cars. Some scientists guess that by 2025, fossil fuels will run out.When people can no longer use gasoline, they may use fuel cells instead. Fuel cells use hydrogen to create energy. People do not need to worry about hydrogen running out, because it is renewable and replaceable. In Washington, D.C., a few people drive cars that run on fuel cells. When these cars need more energy, drivers can go to a hydrogen pump.The first hydrogen pump for the public opened in November 2004, marking an important step toward a cleaner environment. When do fossil fuels pollute the air? A) When we use them to create gasoline. B) When people get them from the underground. C) After being burned to get energy. D) After getting them from a hydrogen pump.
The answer to this question is:
C