saintnicholas[学者]英语中表示推测的常用must和can't
1.对现在情况的推测:must/can'tbe;must/can'tbedoing
Hemustbeinthelibrary.Hecan'tbeintheclassroom.
(他一定是在图书馆.他不可能在教室里.)
Shemustbedoingherhomework.Shecan'tbewatchingTV.
(她肯定是在做作业.她不可能在看电视.)
2.对过去情况或已经发生的情况的推测:must/can'thavedone
HemusthaveleftforBeijing.(他肯定已经前往北京了.)
(她不可能这么早就完成了工作.)