What helps create the climate of Western China as well as the Gobi Desert?

Witch one is it soo it the the question b.a,b,c,d

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.

Where is the world’s shortest commercial runway?