Trace elements in seawater are ________.
A. found in concentrations suitable for commercial use
B. significant components of the total salt content of seawater
C. necessary for many marine life forms
D. in higher concentrations at lower salinities
E. toxic to marine life forms
Answer: C
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Which of the following have contributed most to the increase in atmospheric carbon dioxide levels over the past 250 years?
A) Deforestation and combustion of fossil fuels B) Volcanic eruptions and widespread forest fires C) The thawing of permafrost and habitat alteration for agriculture D) Deforestation and ocean acidification
What does it mean when a solution has a low pH number?
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Well preserved remains of many tiny organisms extend the record of life back beyond 5 billion years
Indicate whether the statement is true or false