Current levels of atmospheric carbon dioxide are
A) remaining high but steady.
B) nearly 400 ppm, higher than they have been in 800,000 years.
C) fluctuating greatly but are starting to increase again after a downward trend in the 1990s.
D) decreasing because surplus carbon dioxide is being absorbed by the arctic permafrost.
B
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The golden tree frog that can only be found in one particular area is an example on a(n) ____________________ species.
Fill in the blank(s) with the appropriate word(s).
Which of the following is produced in the Earth's upper atmosphere as a result of excited atoms and molecules giving off visible light?
A. prominences B. flares C. solar wind D. aurora
The difference between the wilting point and field capacity is approximately equal to
A) wilting point water. B) gravitational water. C) available water. D) hygroscopic water.
Volcanoes are created when lava cools and accumulates over time. What type of rock are volcanoes made of?
A. metamorphic rock B. sedimentary rock C. granite D. igneous rock