Select the correct answer from the list.(1 point)

Question

Between 400,000 years ago until 1950, the levels of carbon dioxide in the atmosphere never exceeded _______ parts per million. Today, carbon dioxide levels have exceeded
______ parts per million.

Answer 1

Between 400,000 years ago until 1950, the levels of carbon dioxide in the atmosphere never exceeded 300 parts per million. Today, carbon dioxide levels have exceeded 400 parts per million.