必须；义务＝have to/have got to (过去式为had to)
(否定为need not/don't have to/don't need to)
My sister is near-sighted. She has to wear glasses for reading.
I can hear you well. You don't have to shout.
It was noisy there. I had to shout. 那里好吵，我得用吼叫的。
On weekdays we must/have to get up early, but on weekends we can sleep late. 周一到周五我们必须早起，但周末我们可以睡到很晚。
Tomorrow is a holiday, so we don't have to/don't need to/need not go to school. 明天是假日，所以我们不用上学。
I've got to/have to/must go now. I have a meeting in ten minutes.
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