to be under necessity or obligation toyou ought to buy him a new book to replace the one you lost
you ought to buy him a new book to replace the one you lost
have (to), must, need, shall, should
will
英语同义词词典收录了63618条英语词条,基本涵盖了全部常用同义词或反义词的辨析及翻译,是英语学习的有利工具。