告密者

(noun, INFORMAL) An informer, or untrustworthy person who reveals secrets deceitfully.

例句

EXAMPLE: When we were children, my little sister was such a snitch that I could never hide anything from our parents.

小時候，我的小妹妹特別喜歡告密，我有什么事都休想瞞過父母。

大錯特錯

(SLANG) To be completely mistaken about something or someone.

EXAMPLE: At first I thought the shy new sales representative would never succeed, but during her first year she made the most sales of anyone in our company, and I knew I was dead wrong about her.

起初，我以為那位靦腆的新銷售代表根本不會成功，然而她在第一年里完成的銷售額公司無人能比，我這才知道當(dāng)初對她的看法大錯特錯了。