Living in the central American desert has its problems, ________ obtaining water is not the least .

Living in the central American desert has its problems, ________ obtaining water is not the least .

A．of which          B．for what           C．as               D．whose

Living in the central American desert has its problems, ________ obtaining water is not the least .

1. A.
   of which
2. B.
   for what
3. C.
   as
4. D.
   whose