1. 使用不定式简化

原句：*The project that was completed on time is very successful.*

简化后：*The project to be completed on time is very successful.*

2. 使用现在分词简化

原句：*The students who passed the exam are celebrating.*

简化后：*The students passing the exam are celebrating.*

3. 使用形容词短语简化

原句：*This is the book which I borrowed last week.*

简化后：*This is the book I borrowed last week.*

4. 使用介词短语简化

原句：*The movie that was directed by the famous director is a masterpiece.*

简化后：*The movie directed by the famous director is a masterpiece.*

5. 移除关系代词

原句：*The city that lies on the river is very beautiful.*

简化后：*The city on the river is very beautiful.*

6. 使用that简化（限定性定语从句）

原句：*The letter which I received yesterday was very important.*

简化后：*The letter I received yesterday was very important.*

说明：

不定式简化适用于定语从句的时态与主句同时或滞后于主句的情况，需注意动词的及物性。- 现在分词简化用于主动语态的定语从句，避免重复主语。- 形容词/介词短语可替代整个定语从句，使句子更简洁。- that简化仅限限定性定语从句，且先行词被唯一确定。通过这些方法，可以有效地简化复杂的定语从句，提升句子的流畅性。