The word "enveloped" in line 6 is closest in meaning to ______.
A. surrounded
B. changed
C. escaped
D. characterized
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The author uses the word "Or" in line 25 to
A. criticize the previous suggestion
B. provide unrelated information
C. propose a similar idea
D. suggest an alternative
According to the passage, outgassing eventually led to all of the following EXCEPT ______.
A. increases in the carbon dioxide content of sedimentary rocks
B. the formation of bodies of water
C. decreases in the level of nitrogen
D. the formation of clouds
The word "they' in line 8 refers to ______.
A. gasses
B. volcanoes
C. steam vents
D. rocks
The passage suggests that oxygen remained in the atmosphere because ______.
A. it was caused by outgassing
B. it was heavier than hydrogen
C. hydrogen became trapped in limestone
D. rays from the sun created equal amounts of hydrogen and oxygen ______.
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