Many scientists believe that the current period of global warming is related to increased levels of
A. carbon dioxide in the Earth's atmosphere.
B. nitrogen in the Earth's atmosphere.
C. hydrogen in the outermost layer of the Earth's atmosphere.
D. radon being released from the Earth's soil.
Increased levels of carbon dioxide in the Earth's atmosphere is the most widely accepted reason for global warming. Most scientists believe this theory and current research has proven it to be true.
