must与have to的区别,过去完成时与过去时的区别.

must和have to 都可以用做情态动词，后面直接接动词原形 must:是必须的意思 must: (1) aux. 必须，需要 word to tell someone what to do,word that tells what is necessary [例句] We must be going now. 我们现在得走了。 Mistakes must be criticized. 有错误就得批