It isn't actually known how many sites there are across Australia where rock art can be found—but unfortunately, we do know that much of the art is being lost to us.

目前还不知道在澳大利亚有多少地方能够发现这种岩石艺术；但不幸的是，我们知道有很多艺术作品正在消失。

youdao

I've known him for years, but I still don't know what pushes his buttons.

我已认识他多年，可还是摸不透他的脾气。

《牛津词典》

I know a sculptor who swaps her pieces for drawings by a well-known artist.

我知道有个雕塑家用她自己的作品去换一位著名画家的画作。

《柯林斯英汉双解大词典》

A navigator needs to know what time it is on his ship and also the time at another place of known longitude -- at the very same moment.

VOA: special.2010.07.14

I don't know a word of Russian, and so I actually try to avoid using the rather well-known Russian equivalents for these terms because I feel like an idiot.

我不懂俄语，所以我不用俄语读,而就用这个英语中通行的俄语替代词,这样感觉是不是挺傻的。

耶鲁公开课 - 文学理论导论课程节选

I would guess that's pretty much, you know, apart from, you know, all the usual, well-known things.

我觉得这些差不多了，加上那些众所周知的地方的话。

鲜为人知的名胜 - SpeakingMax英语口语达人

Mo Udall wanted to know if a well-known entertainer could perform at an event for his 1976 Democratic presidential campaign, or if he had to pay with campaign funds.

WSJ: Designer Gear for Obama Raising a Ruckus

But recently an independent committee monitoring Pfizer's two big studies of the drug, know known as PF-3512676, took a scheduled look at the data.

FORBES: Pfizer Stops Developing Coley Cancer Drug

So, all I know about it is the kind of well-known buzz about it, which is that it's Will Smith's first, you know, serious role.

NPR: Let's All Go to the Lobby: Holiday Movie Preview