必须 一定 可以 应当 很可能中释
Warm clothes are a must in the mountains..御寒衣物在山里是必不可少的。
must be,一定;一定要;肯定是
must have,必须拥有;非有不可
must have been,一定(对过去事实肯定的推测)
must have done,必定做了…(表示对过去的推测)
must be going,该告辞了;必须去
must be off,[口]该走了
must needs,偏要;偏偏
must be valid,必须实事求是