Recent evidence from polar ice core analysis shows that, until now, carbon dioxide levels have never exceeded ______________ ppm in the last several hundred thousand years.
A) 25
B) 1000
C) 200
D) 300
E) 500

Question

Quizplus · Accepted Answer

Recent evidence from polar ice core analysis shows that, until now, carbon dioxide levels have never exceeded 300 ppm in the last several hundred thousand years.

Recent Evidence from Polar Ice Core Analysis Shows That, Until