There are so many people in your house. What are they doing?
We are having a party. I am the host and my wife is the hostess.
Are they your guests?
Yes, they are. They are all my friends.
Who is that man?
He is Professor Zhang. He is a Chinese teacher. His wife is a teacher, too. Their daughter is a college student.
Who is that young man?
He is her boyfriend. He is a young doctor. His name is Karl Black.