Rain forests help slow global warming because
a. plants remove oxygen from the air and expel carbon dioxide.
b. they provide protection from acid rain for humans and animals.
c. plants remove carbon dioxide from the air and expel oxygen.
d. they provide a greenhouse effect that encourages other plants to grow..
Question 2
Experts estimate that the current atmospheric concentration of carbon dioxide is how much higher than it was 250 years ago?
a. 7 percent
b. 12 percent
c. 35 percent
d. 42 percent
