有一读者问： 以下4个分裂句哪些正确？哪些不正确？ who可否被that取代？
(1)It's I who am a teacher.
(2)It's me who am a teacher.
(3)It's I who is a teacher.
(4)It's me who is a teacher.
上述句（1）是当代规范英语；句（2）为非正式英语；句（3）与句（4）虽不错，但在当代英语中较为罕见。who可以被that所取代，但that似乎还不及who普遍，如：
(5)It's John that wore his best suit to the dance last night.
分裂句在传统语法中唤作“强调结构”。
