Multiple Choice
Which is true of the level of C in our atmosphere?
A) It is reached 400 ppm in 2013.
B) The rate of increase leveled out in 1976.
C) The level of C was much higher in 1955 than today.
D) The level of C is decreasing at 3.1% per year.
Correct Answer:

Verified
Correct Answer:
Verified
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