情态动词表示推测must一、对现在情况的推测，问句部分用主动词（do,be)一般现在时的适当形式。若是现在进行时，问句部分用现在进行时的适当形式表示。若是therebe结构，问句用isn‘t/aren’tthere。如：1)Hemustbethere,isn'the?2)Hemusthaveabigfamily,doesn'the?3)Hemustbewaitingoutside,isn'the?4)Theremustbesomestudentsintheroom,aren'tthere?二、对已发生的过去情况的推测，若陈述句谓语部分有“musthavedone”，而且有表示过去的时间状语，问句部分用didn't；若没有表示过去的时间状语，问句部分用haven't或hasn't。如：1)Theymusthavegonetherelastnight,didn'tthey?2)Theymusthavearrivedbynow,haven‘tthey?（根据bynow来判断）3)TheymusthavebeentotheGreatWall,haven'tthey?三、若是被动，应按被动结构来处理。如：1)Theroommusthavebeencleanedyesterday,wasn'tit?2)Theroommusthavebeencleaned,hasn'tit?四、若句中有表示过去完成时的时间状语，问句部分应用hadn't.如:Theymusthavelearnt5000Englishwordsbytheendoflastterm,hadn'tthey?(本题中must表推测，如果将它去掉，还原为真实句就是Theyhadlearnt5000Englishwordsbytheendoflastterm.因此，反意问句是hadn't）Theend
