You must be mistaken.
你一定搞錯了。
must的意思是“必須”,比如下命令時(shí)老板有時(shí)會很強(qiáng)硬地說,
"You must finish this book before this weekend."
(你必須在周末前完成這本書。)
在下面的這句話里must的意思有些變化,有了很強(qiáng)的推測語氣,
"He must have passed the exam, because he was so happy the whole day."
(他一定已經(jīng)通過考試了,因?yàn)樗於寄敲锤吲d。)