How important is it for a country to protect its border? Why?

The last photo u wonder what is this telling me to do?

Most of earths fresh surface water is found in

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.