Complete each sentence using the correct ending from those listed below.
a. A catalyst is
b. Chemical reactions can only happen when
c. Concentration, surface area and temperature can all affect
d. An enzyme is
e. The activation energy is

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.