从句中需要用到谓语来使从句完整.剧中that 做主语,talking with只是一个现在分词结构,需要be动词is来是句子结构完整.is talking with 才构成完整的谓语.
希望能帮到你.难道该句的从句中“my teacher”不是主语？the man that is talking with my father是主语teacher 是宾语可不可以把that删掉，加上who is 这样的句子正确吗？正确，严格来说用who is更妥帖