The chairman told the speaker that she ___ to speak a little louder so as to make herself _____. [    ]

A. was expected; heard  

B. had expected; hear  

C had hoped; hear  

D. was hoped; heard

油区检修应尽量使用有色金属制成的工具，如使用铁质工具时，都应采取防止（）的措施，例如涂油、加铜垫等。

A.碰撞；

B.产生火花；

C.发生弧光