After ____seemed an endless effort,the patient was finally able to take a normal walk

题目

After ____seemed an endless effort,the patient was finally able to take a normal walk
A that B what C it D which

答案

C
因为这个句子的意思是:看起来这是一个无尽的努力后,病人终于能够正常走路．
所以it所表示的意思是这,我的理由是it作一个形式主语吧,在seem也是一个动词,前面要用一个主语．
which 和what首先就可以排除,如果that在这里作重句的话也不通,因为that用来引伸一个重句前面应该一个句子在前加that连接后一个句子,不会有这样的形式的．所以也可以用排除法来做这道题嘛．
其实我也是业余的．．．．．．