Unlike saltwater, freshwater
a. can erode rocks
b. can be stored in reservoirs
c. is needed to keep most plants alive
d. makes up most of the water on earth

What is the mercury length of time for one revolution around the sun?

How would i answer this for an exam?

Which of the following is not a challenge to instituting sound global environmental policies? a. most changes are inexpensive and easy to implement. b. elected leaders who support unpopular environmental issues often are not re-elected. c. economic considerations outweigh environmental ones in many societies. d. there is no way to enforce international environmental agreements.