主句一变，从句为什么也要跟着变？
🧠 一、什么是“时态一致”？
先看一个典型错误：
❌ He said that he is tired.
✔️ He said that he was tired.
📌 原因很简单：
👉 主句是过去时，从句通常也要向过去“靠拢”。
这就是宾语从句中的时态一致原则。
⏰ 二、主句是现在时：从句“自由发挥”
当主句是 一般现在时 / 现在完成时 时，从句的时态不受限制，只需符合事实。
📘 示例：
- I think that she is right.
- I believe that he will succeed.
- We know that the earth moves around the sun.
📌 结论：
👉 主句现在，从句看事实。
⏳ 三、主句是过去时：从句整体后移
当主句是 一般过去时，从句时态通常要“退一步”。
📗 常见对应关系：
- 现在 → 过去
- He said that he was busy.
- 将来 → 过去将来
- She told me that she would come.
- 现在完成 → 过去完成
- They thought that he had finished.
📌 这是考试中最常考的一组规则。
🧱 四、一个重要例外：客观事实不后移
如果宾语从句表达的是 客观事实、真理或长期不变的情况，
👉 即使主句是过去时，从句也不变。
📘 示例：
- The teacher said that water boils at 100°C.
- He explained that the sun rises in the east.
⚠️ 易错提醒：
不是“老师说的时间”，而是“事实本身的时间”。
⚠️ 五、写作中最常见的 3 个错误
❌ She said that she will help me.
✔️ She said that she would help me.
❌ He thought that the test is difficult.
✔️ He thought that the test was difficult.
❌ The scientist said that the earth moved around the sun.
✔️ The scientist said that the earth moves around the sun.
👉 错误根源：
只看主句，不判断信息属性。
✍️ 六、写作应用：让叙述更“像英语”
🔹 原句（中式思维）
He said he is very nervous.
🔹 修正后
✅ He said he was very nervous.
🔹 写作升级
He admitted that he was very nervous before the interview.
📌 写作建议：
转述他人话语时，时态一致是“第一道门槛”。
📝 七、练习任务（时态判断）
请选出正确表达：
- She said that she ___ (finish) the work already.
- He believed that the plan ___ (fail).
- The teacher said that light ___ (travel) faster than sound.
👉 参考答案：
- had finished
- would fail / had failed
- travels
很多写作扣分，并不是因为词汇不高级，而是时态不稳。
在 李校来了英语 的句型与时态训练中，系统会自动识别主从句关系，提醒你是否需要“时态后移”，帮助你把最容易丢分的地方变成最稳的得分点。
