Why do ethnicities engage in ethnic cleansing and genocide?

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.

Suppose that the sun shrank in size but that its mass remained the same. what would happen to the orbit of the earth?

Which phrases describe air density? check all that apply