answer: #Person2# states the purpose of the visit to the United States to #Person1#.
documents: #Person1#: Why don't you sit down? Now, there are several questions I must ask you if you don't mind.
  #Person2#: Not at all. Go ahead.
  #Person1#: What is the purpose of your visit to the United States?
  #Person2#: I am going to attend a conference on air pollution. It will be held in the first two weeks of February at the University of California.
  #Person1#: The University of California?
  #Person2#: Yes, here is the official letter of invitation.
  #Person1#: I see. Fine. When do you want to go?
  #Person2#: I'd like to leave in mid-January if my passport is ready by then.