What are the people in the house doing?

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