as sharp as a needle 异常精明；十分精明

【例句】
The child was as sharp as a needle and soon began to use different words.
这孩子非常聪明，很快就开始运用不同的的词汇了。

One doesn't need to be as sharp as a needle to see that that story doesn't fit the facts.
一个人尚有头脑就可看出那种说法是不符合事实的。