是这样的,当that /who在从句修饰和先行词是宾语时,可以省略。但做主语时,绝不可略去。 e.g. I am the guy (that / who ) you know.这里做you know 的宾语 即 you know the guy ,因此是可以省略的。 I am the guy who did that. 在这里guy 是从句who did that的主语,即the guy did that。 不可以省略。
当that & who 在定语从句中充当宾语时可以省略;充当主语时则不可以省略。 eg: The book that I like best is ... that 是like 的宾语,所以可以省略; The girl who is in charge of the department is ... who 是定语从句中的主语,所以不可以省略。