A、His roommates’ dialects are difficult to understand. B、His roommates come back to the dormitory at midnight. C、He quarreled wi

M: I really can’t stand them any more！
W: Who? What happened?
M: (19) My roommates. Two of them keep talking till midnight and make it impossible to get to sleep.
W: I know how you feel. It’s never easy to live with inconsiderate roommates. I once had a roommate who never cleaned the dormitory or fetched water.
M: So what did you do with her?
W: At first I tried to ignore it because I didn’t want to cause anything unpleasant. But things didn’t
become any better. Suddenly one day I broke out, and said something like " My dear fellow, I really appreciate it if you remember to clean the room once in a while. "
M: Oh, no. (20) You’ve got to be careful with complaints, especially when it comes to your roommates. Anyway you meet each other every day.
W: (20) That’s what I’ve learned from our quarrel and the subsequent coldness between us. Now I realize that I should have put it nicely or casually, something like " Hi, Cindy, it’s your turn to clean the dormitory today. "
M: Perfect. It’s hard to take offense at something like this. (21) Maybe we should learn tolerance and understanding.
W: (21) That’s right. We should bear in mind that we all have shortcomings, or rather peculiar habits. When I come to think of Cindy, she’s really a nice girl except being forgetful and careless.
M: I guess you are right. What would you do if you have roommates chatting at bedtime every night?
W: I would talk it over with them, of course. But I would remember I breathe noisily in my sleep and often keep them awake half the night as well.
M: You do?
W: No, just an example.
19. What problem is bothering the man?
20. What lesson does the woman learn from her experience with her roommate?
21. What is their common conclusion about roommate problems?