If CFCs have not been widely used since the late 20th century, why are they considered a major greenhouse gas in the 21st century?
A) Although they have been banned, they are being use illegally
B) CFCs are released by a number of natural processes, such as volcanoes
C) Greenhouse gases such as methane will break down into CFCs
D) CFCs can stay in the atmosphere for decades
Question 2
How can agriculture be responsible for increasing the amount of methane in the atmosphere?
A) Crops like corn and soybeans add methane to the atmosphere
B) Methane is emitted by bacteria in the gut of agricultural animals, such as cattle and sheep
C) Overtilling the land will cause the soil to break down and release greenhouse gases
D) Fumes from liquid fertilizer are opening holes in the ozone
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