Here, everyone knows your business, and everything else about you.
I've never met a man who knew his business better.
But since you are here, I would like to know your business.
There was also one who had not, and perhaps she knew her own business best.
Clearly we were expected, and everyone but me knew our business.
"But I will say that they seem to know their business."
Well, it was always nice to deal with people who knew their business.
If he knows his business, he'll get a new girl.
It would be different now; he knows his business better!
She would have given a great deal to know their business, but not at the cost of being recognized.