阅读理解。 Most people in Britain live in small family groups. More than a quarter of houses in Britain have only got one person in them. Some of these are old people but some are people of twenty to thirty who choose to live alone. 35% of houses have two people in them, and another 17% have three people. 15% have four people in them, and the other homes have five or more. The families in Britain are small. It is unusual for parents to have more than two children. When children are about eighteen or nineteen, they leave their parents' home, and they often go to a different city. Sometimes they only visit their parents two or three times a year. 1. How many houses in Britain have 3 people living in them? A. 8% of houses. B. 15% of houses. C. 17% of houses. D. 35% of houses. 2. At what age do children in Britain usually leave their parents' home? A. About 18 or 19. B. About 20 or 21. C. About 25 or 26. D. About 30 or 31. 3. What do you think the passage is? A. An instruction. B. A report. C. A play. D. A joke. 4. What does the passage mainly tell us? A. Young people in Britain. B. Old people in Britain. C. Families in Britain. D. The population in Britain. 5. According to the passage, which of the diagrams is right?