定义 / 说明
在 say/think/know/believe/hope/be sure 等动词后的从句里，that 常可省略且不改基本意义。这种省略在口语和中性写作中很常见。保留 that 有时会更正式、更清晰，或在长句中更利于处理层级。C1 关注点通常不是“能不能省”，而是“在这个文体里是否该省”。某些位置（尤其介词后）并不能直接省掉 that。
关键规则
- 许多报告/思维动词后 that 可选：I think (that) you are right.
- 会话和直白文字中省略很常见。
- 长句或多重从句中，保留 that 常能减少歧义。
- 某些结构里省略不自然或不可行；介词后通常需改结构。
- 当 that 作关系从句主语时不能省：The book that won the prize。
例句
- I think (that) it's fine. - 我觉得这没问题。
- She said (that) she was tired. - 她说她累了。
- I'm sure (that) he knows. - 我确信他知道。
- We hope (that) the plan will work. - 我们希望计划能奏效。
- The report showed that sales had fallen. - 报告显示销量下降了。
常见错误
- ❌ The book won the prize was expensive. -> ✅ The book that won the prize was expensive.
- ❌ It depends that we have enough time. -> ✅ It depends on whether we have enough time.
- ❌ She said me that to wait. -> ✅ She told me to wait. / ✅ She said (that) I should wait.