—The duty of Project Hope is to help poor children,  isn't it?            

—Yes,  it has built many schools________are for those children.        [ ]

A. what      

B. that      

C. who        

D. where

建筑防水沥青嵌缝油膏有很好的气候适应性，100℃不流淌，20℃不脆裂。