Craters visible on the moon's surface provide further evidence of
a) frequent asteroid impacts.
b) periodic volcanic eruptions.
c) frequent landings of spacecraft.
d) the long-ago presence of ice on the moon.

What effect would average population growth have on land usage? a. urban use of land would rise to more than 30 percent of available land. b. industrial use of land would rise to more than 30 percent of available land. c. the percentage of available land used as cropland would stay the same. d. cropland would fall to about 10 percent of available land.