Earth has been gradually warming over the past few decades. Based on a great deal of evidence, scientists believe that this warming is caused by
A. the increase in forest fires during recent years.
B. human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere.
C. the human release of chemicals called CFCs into the stratosphere.
D. the fact that our politicians spout a lot of hot air.
Answer:B
Earth has been gradually warming over the past few decades. Based on a great deal of evidence, scientists believe that this warming is caused by
A. the increase in forest fires during recent years. B. human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere. C. the human release of chemicals called CFCs into the stratosphere. D. the fact that our politicians spout a lot of hot air.