have to / has to / had to
“不得不、必须”：has to 跟第三人称单数，had to 是过去；don't have to = 不必，mustn't = 禁止。
例句
- She has to get up early every day.她每天都得早起。
- You don't have to come early tomorrow.明天你不必早来。
- You mustn't smoke here.你不许在这里吸烟。
讲解
学会以后，你能
- 说“我得……”“他不得不……”“昨天我只好……”
- 分清“不必”和“禁止”
- 问“我必须……吗？”
构成
have to / has to / had to + 动词原形
I / you / we / they have to …
he / she / it has to …
过去（所有主语）：had to …
She has to get up early every day.
她每天都得早起。
I had to walk home yesterday.
昨天我不得不走路回家。
否定
don't have to = 不必
You don't have to come early tomorrow.
明天你不必早来。（来也可以，但没必要）
She doesn't have to work on Saturdays.
她周六不必上班。
mustn't = 禁止
和 don't have to 意思完全不同
You mustn't smoke here.
你不许在这里吸烟。
You don't have to smoke here.（意思是“你没必要在这里吸烟”，完全不是禁止！）
疑问
Do / Does / Did … have to …?
Do I have to pay now?
我必须现在付钱吗？
Did you have to work late yesterday?
你昨天必须加班吗？
常见错误
He have to go.He has to go.
第三人称单数用 has to。
Do I must pay now?Do I have to pay now?
must 不和 do 一起用；要么 Must I …?，要么 Do I have to …?
Yesterday I must stay at home.Yesterday I had to stay at home.
must 没有过去式，过去的“必须”用 had to。
He doesn't has to go.He doesn't have to go.
doesn't 后面用原形 have。
练习要点
1. have to / has to / had to
第三人称单数用 has to；过去一律用 had to。
- She has to get up early every day.她每天都得早起。
- I had to walk home yesterday.昨天我不得不走路回家。
2. don't have to（不必）和 mustn't（禁止）
don't have to 表示没必要；mustn't 表示不允许。
- You don't have to come early tomorrow.明天你不必早来。
- You mustn't smoke here.你不许在这里吸烟。
3. 疑问 Do I have to …?
疑问句用 do / does / did 开头，后面接 have to。
- Do I have to pay now?我必须现在付钱吗？
- Did you have to work late yesterday?你昨天必须加班吗？
练到脱口而出
围绕这 3 个要点的小练习，每答一题立刻批改。免费开始。