听第10段材料，回答第17至20题。

　　17. Why did the speaker become busy with housework last month?

　　A. Because she liked cleaning rooms.

　　B. Because she wanted to sell her house.

　　C. Because she waited for the old couple.

　　18. When did the old couple visit the speaker's house?

　　A. In the morning. B. In the afternoon. C. In the evening.

　　19. How did the speaker feel when the old couple looked around the house?

　　A. She was pleased. B. She was embarrassed. C. She was surprised.

　　20. What can we learn after listening to the passage?

　　A. The old couple had lived in the speaker's house before.

　　B. The speaker's house was untidy all the time.

　　C. The old couple's house might not be very tidy.