—You’ve made great progress in your studies of English, haven’t you?
—Yes, but much ____.
A. remains to do　　　　　　　B. is remained to do
C. remains to be done　　　　 D. is remained to be done
选哪个？
并且愿闻其详

答案选C
remain: be left to beseen,done,said,etc.有这个解释我们可以判定remain 本身就表示被动了，所以不能再用被动语态，所以选项B、D排除 。在这个句子里much时代词，指学习英语中的很多事情，much 做主语，谓语动词用单数，因为much代指的事情，所以事情当然是被人来做的了，所以用被动，所以选remains to be done,有道类似的高考题：going abroad is good for the old couple,but whether they will go abroad remains to be seen.你也可以参考这道高考题