Clouds continually are pulled to the ground by gravity. Why do they stay aloft?
A. New cloud droplets continually replace those that fall to Earth's surface.
B. Water evaporating from Earth's surface presents an opposing force to the falling cloud droplets.
C. Updrafts of air oppose the gravitational force.
D. Clouds weigh so little that they fall too slowly to be noticed.
Answer: C
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A. nuclear breeder reactor B. pressurized-water reactor C. boiling-water reactor D. light-water reactor
According to this graph, which shows water balance for the Ogallala aquifer, which of the following statements are true?
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Amongst the biogeochemical cycles, which one can be said to operate rapidly?
What will be an ideal response?