We had not realized how much people appreciated the library‟s old borrowing policy until we received complaints once it had been ________.
句意： 在旧的规定被废弃时我们收到了许多投诉， 在此之前我们未曾意识到人们对图书馆过去的借书政策有多少了解。 supersede取代。 continue继续。imitate模仿。 administer管理。 因此， 本题的正确答案是A。