Native English spekers, could you please help me with these issues?

Are these sentences correct: a) "Global warming is primarily a problem of too much carbon dioxide (CO2) in the atmosphere which produces a greenhouse effect. b) "As we burn fossil fuels like coal, oil and natural gas for energy, carbon spreads in the atmosphere, in harmful amounts." c)... show more Are these sentences correct:


a) "Global warming is primarily a problem of too much carbon dioxide (CO2) in the atmosphere which produces a greenhouse effect.

b) "As we burn fossil fuels like coal, oil and natural gas for energy, carbon spreads in the atmosphere, in harmful amounts."

c) "Cutting down and burning forests to create pastures and plantations have just aggravated the problem, since plants, by absorbing carbon from the atmosphere, usually decrease its amounts."
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