全国大众英语测验语法——比较haveto和must
1)两词都是'必需'的意思，have to默示客不雅观的需要， must默示说话人主不雅观上的不雅观点，既主不雅观上的需要。
My brother was very ill, so I had to call the doctor in the middle of the night.我弟弟病得很凶猛，我只得半夜里把年夜夫请来。(客不雅观上需要做这件事)
He said that they must work hard.他说他们必需勉力义务。（主不雅观上要做这件事）
2)have to有人称、数、时态的转变，而must只要一种形式。但must可用于直接引语中默示过往的需要或义务。
He had to look after his sister yesterday.
）在否定构造中： don't have to默示"不用"
mustn't默示"克制"，
You don't have to tell him about it.你不一定要把此事通知他。
You mustn't tell him about it.你一定不要把这件事通知他。