While our city tries   impatiently to change its appearance by tearing down old   buildings, more and

more citizens are suggesting ways to  ____ the historically important architecture.    [ ]

A. decorate  

B. develop    

C. preserve    

D. advocate

钻进中，当孔内瓦斯压力增高，出现顶钻、蹩泵现象时，应加压钻进。