Suppose we had a device that allowed us to see Earth's interior. If we looked at a typical region of the mantle, what would we see happening?
A) not much—on human time scales, the mantle looks like solid rock
B) hot molten rock rising upward throughout the mantle and cool, solid rock falling downward
C) a rapid, up-and-down churning of the material in the mantle
D) dense metals falling downward while low-density rock rises upward
A
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Which of the following statements about sewage is not true?
A) All municipalities must treat sewage the same way. B) All municipalities must treat sewage. C) Once treated, sewage is released to the environment. D) Treated sewage becomes drinking water downstream. E) None of the above are true.
The wavelength of a periodic wave is 0.800 m. If the frequency is 400 Hz, then what is the magnitude of the k vector of the wave?
A. 8.56 
B. 7.85
C. 7.02
D. 6.35
E. 5.98
When the spool is pulled to the left, it accelerates toward the
1) right, 2) left, which illustrates the fact that 3) for every force there is an equal and opposite reaction force. 4) net force and acceleration act in the same direction.
Which of the following statements applies in the final moments of the life of high-mass stars?
A. Around their cores, they have a series of nested shells, each made of a heavier element than the one surrounding it. B. The core temperature is about 2 billion degrees. C. Their outer layer is mainly hydrogen and helium. D. They have iron cores. E. All of these choices are correct.