He knows what to do. He's been around
他知道該做什么。他閱歷很豐富。
What difference will it make if he knows or not?
他知不知道有什么關系嗎？
I can't help thinking he knows more than he has told us.
我總覺得他沒把他知道的事全告訴我們。
He knows better than to judge by appearances.
他明白得很，絕不會憑表面現象來判斷。
I'm still not totally convinced that he knows what he's doing.
我仍然不完全相信他明白自己在干什么。