I know that he is here. I know he is here. (without "that") He knows where I live. What she sang was a Hungarian folk song. I don't know who that boy is. I don't know whose pen this is. I don't know if Maria is at home or not. I don't know whether or not Maria is at home. I don't know where she lives What she's doing is very interesting. Do you know how old they are? He wants to find out where she was born. What they did was wrong. Could you tell me where the post office is? where the bathroom is? where the bus stop is?