A、Finish her experiment. B、Work on a paper. C、Stay in the library. D、Lie out in the sun. B男士问女士这么早回来做什么，女士说她有论文要写，在沙滩做不了任何深入的研究。

M: Hey, Linda. Looks like you got some sun this weekend.
W: Yeah, I guess so. I spent the weekend at the beach.
M: Oh, yeah? That’s great! Where did you stay?
W: Some friends of my parents live out there. And they invited me for as long as I wanted to stay.
M: So, what are you doing back here already?
W: Oh, I have a paper I need to work on. And I just couldn’t do any serious studying_at_the beach.
M: I don’t blame it. So, what did you do out there? I mean, besides lay out in the sun, obviously.
W: I jogged up and down the beach and I played some volleyball. You know, I never realize how hard it is to run on sand. I couldn’t even get through a whole game before I had to sit down. It’s much easier to run on the wet sand near the water.
M: Not to mention cooler. Did you go swimming?
W: I wanted to, but they said the water isn’t warm enough for that until a couple of months from
now. So I just waded in up to my knees.
M: It all sounds so relaxing. I wish I could get away to the beach like that.
W: It looks like you could use it. Don’t tell me you spent the weekend in the library again.
19. How did the woman spend the weekend?
20. What does the woman have to do after she comes back?
21. Why did the woman have to stop playing in the volleyball game?
22. Why didn’t the woman go swimming?