What sea lies between Australia and Melanesia?

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.

Can someone me with this plz? ! i'm putting 20 points on it!

Over half of the african-american population in the united states live in