Living in Western China certainly has its problems obtaining water is not the least. A. o

问题补充：

Living in Western China certainly has its problems, obtaining water is not the least.

A. of which

B. where

C. as

D. whose

答案：

(答案→)A. of which

B. where

C. as

D. whose

解析：考查定语从句。句中先行词为problem，在定语从句作obtaining water of的宾语，故用关系词which。句意：生活在中国西部有它一定的问题，其中重要的一个就是取水问题。