You should know better than ( to leave ) your little sister

1．know better than+不定式。这种结构意为“不至于”： She knows better than to go alone on such a night。 在这样的夜晚,她不至于连不宜单独外出也不知道。 know better than to do sth。的含义是be wiser,better informed,or more sensible than to do or believe sth。 http://222。187。96。26/Article/Print。asp?ArticleID=24