According to the figure below, approximately how many years ago did oxygen finally get to half its current abundance in Earth's atmosphere?
a. 3 billion years ago
b. 1 billion years ago
c. 0.6 billion years ago
d. 0.25 billion years ago
e. 0.1 billion years ago
c. 0.6 billion years ago
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A store's inventory or a library's card catalog is stored in a(n) ______.
A. portfolio B. database C. briefcase D. linear file
The grooved terrain found on Ganymede is believed to be:
A) systems of faults in the brittle crust. B) flow channels or liquid methane. C) caused by meteor impacts. D) formed with long cracks in its icy crust.
Molecular Bonds: In general, which of the following is usually the strongest bond?
A. hydrogen bond B. van der Waals bond C. ionic bond
Zero degrees on the Celsius scale
corresponds to what reference point? a)the ice point b)the steam point c)absolute zero d)212 degrees Fahrenheit