1) that, which, whom,若在从句中做宾语时可以被省略
例: Mary likes the book( that/ which) her mother bought yesterday.
2) that, which, who在从句中做主语时,“主+系”经常可以同时省略,即 that+ be, which+ be, who+ be可同时省略,转换成形容词短语结构或者 doing, done的非谓语动词结构置于名词后进行修饰
例:
1. Victoria is totally absorbed by the books( that/ which were) written by Dickens.
2. I know the girl( who is) standing there.
3. his book describes some artisans( who were) famous in the past.