语法点：真实条件句 (First Conditional)
真实条件句用来谈论将来很可能发生的情况及其结果：“如果……，就会……”。它由 if 引导的条件从句和主句组成。关键规则是：if 从句用一般现在时表示将来，主句用一般将来时 will + 动词原形。if 从句可以放在句首（后面加逗号），也可以放在句末（不加逗号）。本课讲停车与交警的故事，三处用真实条件句说明“如果乱停车会怎样”。
结构
| 位置 | 结构 | 例句 |
|---|---|---|
| if 从句在前 | If + 主语 + 一般现在时, 主语 + will + 动词原形 | If you park your car in the wrong place, a policeman will find it. |
| if 从句在后 | 主语 + will + 动词原形 + if + 主语 + 一般现在时 | You will be lucky if he lets you go. |
| 否定 | If + 主语 + do not / does not…, 主语 + will not… | If you do not pay attention, you will get a ticket. |
| 主句用情态动词 | If + 一般现在时, 主语 + can / cannot + 动词原形 | If you receive a request like this, you cannot fail to obey it. |
注意：if 从句中主语是第三人称单数时动词要加 -s（if he lets…）。
课文中的例句
- [句 1] If you park your car in the wrong place, a traffic policeman will soon find it. — 标准结构：if + 一般现在时，主句 will + 动词原形。
- [句 2] You will be very lucky if he lets you go without a ticket. — if 从句放在句末，不加逗号；lets 是第三人称单数。
- [句 6] You will enjoy your stay here if you pay attention to our street signs. — 用真实条件句提出礼貌的要求。
- [句 7] If you receive a request like this, you cannot fail to obey it! — 主句用情态动词 cannot 代替 will。
补充例句
- If you park here, you will receive a ticket. — 如果你停在这里，你会收到罚单。
- If the policeman is polite, you will obey him. — 如果警察很有礼貌，你会听他的。
- You will not find a No Parking sign if you look at the wrong place. — 如果你看错地方，就不会看到禁止停车的标志。
易错点
- ❌ If you will park your car here, a policeman will find it. → ✅ If you park your car here, a policeman will find it. — if 从句用一般现在时，不能用 will。
- ❌ If he let you go, you will be lucky. → ✅ If he lets you go, you will be lucky. — if 从句主语是第三人称单数，动词要加 -s。
- ❌ If you receive a request like this, you obey it. → ✅ If you receive a request like this, you will obey it. — 主句要用 will（或情态动词）表示将来结果。
- ❌ You will enjoy your stay here, if you pay attention to our signs. → ✅ You will enjoy your stay here if you pay attention to our signs. — if 从句在句末时通常不加逗号。