单选题
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.无
A、
was made
B、
would have been made
C、
has been made
D、
had been made
【正确答案】
D
【答案解析】
句意：只有在人们对于开发和利用电流取得了一些进步后， 人们才意识到电磁的重要性和巨大潜力。 主句用的是it was， 过去式， 而取得进步是在此之前， 因此要用过去完成时， 再由句意可知这里是被动， 因此D项正确。
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