听力原文：W: This food is terrible! I can't even finish my dinner.
M: I know, you think with all the money we paid for room and board, the university could hire a better food service. Where are you heading next？
W: I'm going over to the student recreation center to play some bridge.
M: You are spending your time on a card game？
W: Not just a card game. It's one of the most strategic games.
M: So I have heard. Don't you play with a partner？
W: Yeah! Four people play, two against the other two.
M: So, you try to play in cooperation with your partner？
W: Actually, the cards of one of the four players are turned face-up. That player is called the dummy.
M: I wouldn't want to be called that. When you are the dummy, what do you do while the cards are being played？
W: Anything you want. Sit there and study, shuffle another deck, get snacks for everyone... I like to stand behind my partner and watch. That is very interesting.
M: You know, I've heard that bridge is habit-forming. You should be careful not to play so much that you don't get your studying done.
W: Don't worry about me. I only play cards on Thursday after dinner, and sometimes when they need a fourth player. If you like, I could teach you.
M: Thanks, but I have a pretty heavy workload this semester. I already spend my evenings doing things I don't really know how to do yet.
W: I know you are busy, but sometimes you need to have a rest.
Questions 19 to 22 are based on the conversation you have just heard.
19. How does the woman plan to spend her evening？
20. What will the woman probably do if she is the dummy？
21. What does the man warn the woman not to do？
22. Why doesn't the man accept the woman's offer？
(23)

A. Playing cards.
B. Preparing snacks.
C. Studying with a partner.
D. Learning how to design bridges.