___certain doubt among the student as to the necessity of the work A.they existed B.there existing
问题描述：
___certain doubt among the student as to the necessity of the work A.they existed B.there existing
C.thereexisted D.IT exist 选什么 喂什么BD不可以
答
C.There existed 是的
there exist=there be,有着,存在的意思.B错在existing不对,不能用分词,因为要做谓语；D.IT exist 错在没有这样的用法.