sharp as a tack 机灵的（成语）

英文释义
(IDIOM) Very intelligent.

例句
Our accounting consultant may be old but she's sharp as a tack, and in only a few minutes she found a number of errors in our accounts.

我们的会计顾问虽然年老，但是非常机灵，她在几分钟内就发现了账目中的很多错误。