Not "I have be at school at eight." — say "I have to be at school at eight.". 动词前面要说 have to，别漏了 to。
试一试: Amina: Can I leave these boxes in the hall? Lars: No. The landlord checks the halls every week. We ___ keep them in our apartments. 选出 Lars 会说的话。 (have / have to / don't have to) 答案: have to — 房东每周都查楼道，所以把箱子放回屋里不是可以选的事：Lars 说 have to + keep。只用 have 少了 to，而 don't have to 会变成“可以不做”。
he、she、it：用 has to
主语是 he、she 或 it 的时候，要说 has to。
He has to leave at seven.
The doctor has to see ten people today.
Not "He have to leave at seven." — say "He has to leave at seven.". he、she、it 后面要说 has to。
试一试: Amina: Why is the man in 2B so busy? Lars: He ___ move out on Friday. 选出 Lars 会说的话。 (have to / has / has to) 答案: has to — 主语是 he，所以说 has to + move。have to 配 I、you、we、they，而只用 has 少了 to。
don't have to + 动词
don't have to + 动词，表示这不是规定。你可以做，也可以不做。
You don't have to call me. I'm fine.
We don't have to cook tonight.
试一试: Amina: The library closes at eight. Is my book late? Lars: No. You ___ take it back today. You have two weeks. 选出 Lars 会说的话。 (don't have to / have to / doesn't have to) 答案: don't have to — Amina 还有两周时间，所以今天还不还书由她自己决定：don't have to + take。have to 意思是今天是最后一天，而 doesn't have to 配 he、she、it，不配 you。
he、she、it：用 doesn't have to
主语是 he、she 或 it 的时候，要说 doesn't have to。
She doesn't have to wear a uniform.
He doesn't have to work on Friday.
Not "She don't have to go." — say "She doesn't have to go.". he、she、it 后面要说 doesn't have to。
试一试: Amina: Does your friend go to a classroom for her English class? Lars: No. She ___ go. The class is online. 选出 Lars 会说的话。 (don't have to / doesn't have to / has to) 答案: doesn't have to — 课是在网上上的，所以不用去教室；主语是 she，要说 doesn't have to。don't have to 配 I、you、we、they，而 has to 就等于让她非去教室不可。
Do you have to? Does he have to?：怎么提问
想问是不是有规定，就说 Do you have to + 动词？主语是 he、she、it 的时候，说 Does he have to + 动词？
Do I have to buy a ticket? Yes, you do.
Does she have to study tonight? No, she doesn't.
Not "Does he has to go?" — say "Does he have to go?". does 后面要说 have to，不说 has to。
试一试: Amina: ___ I have to take off my shoes? Lars: Yes, please. The floor is new. 选出 Amina 说的第一个词。 (Does / Am / Do) 答案: Do — 主语是 I，问规定的问句要用 Do 开头：Do I have to take them off? Does 配 he、she、it，而 Am 不能和 have to 连用。
是规定，还是可以选择
你必须去做吗？就说 have to。可以自己选吗？就说 don't have to。
At this school, you have to wear a uniform.
You don't have to wear a tie, but you can.
试一试: Amina: Can I go home now? Lars: Sure. You ___ stay. We can do it tomorrow. 选出 Lars 会说的话。 (have to / don't have to / has to) 答案: don't have to — 明天也可以做，所以留不留下来由 Amina 自己选：don't have to + stay。have to 会让她今晚非留下不可，而 has to 配 he、she、it。