问题描述：
一道牵涉到时态的英语竞赛题.求助大神解释~~
It was only after some progress ____ in the use and development of electric current that men began to realize the importance and possibilities of magnetism.
A.was made B.would have been made
C.has been made D.had been made
It was only after some progress ____ in the use and development of electric current that men began to realize the importance and possibilities of magnetism.
A.was made B.would have been made
C.has been made D.had been made
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