Some scientists hypothesize that earth's ozone layer is being damaged by
a. ultraviolet radiation
c. plant life on earth
b. chlorofluorocarbons
d. global warming

Which of the following is an important principle of how water moves through a watershed? a. most freshwater is in the form of ice. b. small streams flow into larger streams. c. each watershed contains only a single source of water. d. clouds are formed through evaporation and then condensation.