A、Teacher and student. B、Seller and customer. C、Old friends. D、Old classmates. A

W: Hello, Prof. Green. What a nice surprise to meet you here!
M: Oh, dear, Is that you, my little Lin Da? How times flies! We haven’t met for three years.
W: Right. Your class always remains fresh in my mind as I enjoyed it so much. How have you been? I’ve been missing you.
M: I’m fine, dear. You have really grown up.
W: Prof. Green. I’m going to get married next month.
M: What wonderful news! Best wishes on a happy marriage.
W: Thank you, Prof. Green. I’d like to invite you to my wedding. Could you please come?
M: Sure, sure. Lin Da. I’ll also bring you a good present. I’m sure you’ll like it.
W: That’s very kind of you, professor.
Q6. What’s the probable relationship between the two speakers?