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

Question

fill in the blanks
400
300
200
100 for blank one

300
500
550
410 blank 2

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 410 parts per million.