使用代词时请注意其单、复数，主、宾格以及形容词性物主代词和名词性物主代词的用法。
1. He is one of those speakers who make his ideas perfectly clear.
定语从句的先行词是those speakers，为复数，因此从句中的指示代词应为复数，应把his改为their。
2. Whom do you think has left the lights on?
放在疑问句特殊疑问词后的do you think / believe / guess / imagine / suppose等都不参与句子成分。本句中去掉do you think后缺的是
主语，应把Whom改为Who。
3. The boss pretended not to see John and I.
John和I在句中都做的宾语，应把 I 改为me。
4. These books are mine；those in the bag are her.
her是形容词性物主代词，后面应该加名词books，或把her 改为hers。
