China has planned to build the world's largest national park, ________ is expected to replace America's Yellowstone National Park．

1. A.
   which
2. B.
   where
3. C.
   what
4. D.
   as

China has planned to build the world’s largest national park,         is expected to replace America’s Yellowstone National Park. 

A．which       B．where       C．what     D．as