Multiple Choice
According to the figure below,how much has atmospheric carbon dioxide (CO2) increased in parts per million (ppm) in approximately the last 50 years? 
A) from about 310 to 320 ppm
B) from about 360 to 400 ppm
C) from about 320 to 400 ppm
D) from about 380 to 400 ppm
Correct Answer:
Verified
Correct Answer:
Verified
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