By 10,000 years ago, about ________ people inhabited the entire world; today there are over ________.
A. 350,000; 300 million
B. 65 million; 9 billion
C. 5 million; 6 billion
D. 500,000; 1 billion
E. 1 million; 20 billion
Answer: C
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What is the key concept addressed by the question?
What will be an ideal response?
An acid is a substance that, in solution, releases
A. oxygen ions in H2SO4. B. hydrogen ions, for example, HCl. C. —COOR ions from beer. D. chloride ions from NaCl.
Pure water is defined by
A) its ability to serve as a pH buffer in solutions. B) an equal number of H+ and OH- ions. C) a neutral pH of 7, and equal number of H+ and OH- ions, and its ability to serve as a pH buffer in solutions. D) a neutral pH of 7. E) a neutral pH of 7 and an equal number of H+ and OH- ions.
Viruses are not made up of cells. According to cell theory, this means what?
A. Viruses can cause disease. B. Cells can be infected by viruses. C. Cells come only from pre-existing cells. D. Viruses are not living. E. Cells and viruses are the same thing.