asked 127k views
4 votes
The Keeling curve shows that carbon dioxide concentration in Earth's atmosphere

reached _____ ppm in 2013.
a) 250
b) 300
c) 350
d) 400

asked
User Elfoc
by
7.6k points

1 Answer

5 votes
The answer is c) 350 I’m pretty sure
answered
User Aldan
by
7.8k points
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