The school board ruling mandating that physically handicapped students be placed in regular classroom settings whenever possible also assured all children who have a reading problem of special aid. (A) be placed in regular classroom settings whenever possible also assured all children who have a reading problem (B) should be placed in regular classroom settings whenever possible also assures all children that have a reading problem (C) are placed in regular classroom settings whenever possible also assures those children who are having reading problems (D) be placed in regular classroom settings whenever possible also assured children with reading problems (E) should be placed in regular classroom settings whenever possible also has assured all those children with a reading problem 答案是D。我想问的是A和D的区别，A为什么错？
