Lishui City are facing the following development constraints: overall economic strength is not strong, lack of regional cohesion caused by weak radiation, lack of identity for common development caused by “distance”, and the hilly mountainous terrain limits the development of transport infrastructure. Inevitably, Lishui City has to develop _____ based on its natural ecological advantages.
A、heavy industry 
B、high-technology industry 
C、ecological economy
D、export-oriented economy