Multiple Choice
The average annual concentration of atmospheric carbon dioxide has been rising over at least the past 50 years,based on direct measurements.Why? Choose the best answer.
A) Plant respiration rates are higher than rates of photosynthesis.
B) Humans release carbon dioxide into the atmosphere by burning fossil fuels.
C) More carbon dioxide is entering the atmosphere than is leaving it.
D) Wildfires have increased in length and intensity.
E) The greenhouse effect has been increasing.
Correct Answer:

Verified
Correct Answer:
Verified
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