A、Go to summer school. B、Take a vacation. C、Stay at home. D、Earn some money. D选项中的summer school，Take a vacation，Earn some money等

M: I really don’t know what to do this summer. I can’t afford to just sit around, and there don’t seem to be any jobs available.
W: Why don’t you try house-sitting? Last summer my friend Margaret house-sat for the Dodds when they went away on vacation. Mr. Dodd hired Margaret to stay in their house because he didn’t want it left empty.
M: You mean the Dodds paid Margaret just to live in their house?
W: It wasn’t that easy. She had to mow the lawn and water the house plants. And when Eric house-sat for Dr. Cohen, he had to take care of her pets.
M: House-sitting sounds like a good job. I guess it’s a little like baby-sitting — except you’re taking care of a house instead of children.
W: The Student Employment Office still has a few jobs posted.
M: Do I just have to fill out an application?
W: Margaret and Eric had to interview with the home owners and provide three references each. M: That seems like a lot of trouble for a summer job.
W: Well, the home owners want some guarantee that they can trust the house-sitter. You know, they want to make sure you’re not the type who’ll throw wild parties in their house, or move a group of friends in with you.
M: House-sitters who do that sort of thing probably aren’t paid then.
W: Usually they’re paid anyway just because the home owners don’t want to make a fuss. But if the home owner reported it, then the house-sitter wouldn’t be able to get another job. So why don’t you apply?
M: Yeah, I think I will.
Questions 19 to 22 are based on the conversation you have just heard.
19. What does the man want to do this summer?
20. What did the Dodds do when they went away last summer?
21. What is one responsibility the house-sitter probably wouldn’t have?
22. How do home owners determine the reliability of a house-sitter?