High levels of ____ could indicate life on other planets

a. free nitrogen
b. carbon dioxide
c. free oxygen
d. bound nitrogen


ANS: C
Oxygen in itself is a very reactive element. It binds quickly to other materials. Remember, free oxygen
only became abundant in our atmosphere when photosynthetic organisms began producing more.
Thus, if there is a large amount of free oxygen, then there is something present that is replacing it in
the atmosphere. This is likely to be a life-form of some sort. Information can be found in the section
Are There Other Ocean Worlds

Environmental & Atmospheric Sciences

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Globalization of the last 3-4 decades is characterized by a significant increase in all of the following except

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Environmental & Atmospheric Sciences

To calculate sea-level pressure everywhere, we need to correct for:

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Environmental & Atmospheric Sciences