The increase in atmospheric oxygen during the Proterozoic was related to
a. a decrease in worldwide volcanism. d. the appearance of land plants.
b. a decrease in the size of oceans. e. none of the above
c. photosynthesis by cyanobacteria.
C
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Which of these water resources will take the longest to clean itself naturally once polluted by degradable compounds? Assume that the source of the pollution has been eliminated.
A. groundwater B. stream C. river D. lake
In the United States, California and Texas have the largest number of undocumented immigrants
Indicate whether the statement is true or false.
Most precipitation from thunderstorms originates through the collision-coalescence process
Indicate whether the statement is true or false
Savanna grass would most likely be associated with which climate type?
a. ?tropical rainforest (Af) b. ?tropical monsoon (Am) c. ?tropical wet-and-dry (Aw) d. ?semi-arid (BS) e. ?dry-summer subtropical (Cs)