All of the following statements are true of the water cycles EXCEPT:

a. Runoff occurs when excess water flows across the surface. This water can carry contaminants into rivers, lakes, and oceans.
b. Water in reservoirs are used in households, industry, and agriculture. The largest reservoir is Lake Mead on the Colorado River.
c. The oceans contain about 97.25% of all of the water on the planet.
d. Once water vapor becomes liquid it will never be vapor again.