The probable relationship between Mark and Wendy is that they are husband and wife.

M: Wendy, do you have any good idea for remembering new words and expressions in Italian?  I just can’t remember all the things we learn.
W: Um, I do lots of things, but I don’t know if they’d work for you, Mark.
M: Like what?
W: Well, I do things like…um… I stick little notes all over my house with new words.
M: Are you serious?
W: Yeah, I put them on the fridge, on the walls of the bedroom. Just little notes with the words written on them.
M: Wow!
W: And when I’m on the train going to work, I take my notebook and test myself. Why, do you?
M: Well, I tried reading my Italian notes before I went to bed, hoping I’d dream in Italian. But it didn’t really work.
W: I think it’s a good idea to write the words in new sentences that you invent, So you…um…
M: What, you make up the sentences yourself?
W: Yeah, because then it’s easier to remember them. Like if you write sentences about your family or friends, you can remember them better.
M: That’s a good idea. I like that. What else?
W: And I think the key to remembering new words better is to review them regularly. Just keep revising.
M: Like, study them every day?
W: I don’t know about every day, but if you review them often enough and try to use them in class or when you’re writing, then they become a part of your vocabulary.
M: Do you think so?
W: I think so，yeah.