阅读下面短文,从每题所给的A、B、C、D四个选项中选出最佳选项。
Some families live in small towns,others live in big cities. What happens when a family moves(移居)from a small town to a big city?
Joe's family lives in a big house with a garden in a small town. The house is on a quiet street with lots of trees. There's only one school in the town. Joe's family usually walks to some near places because the town is so small.
Joe's mother gets a new job in the city,so the family moves there.
Now they live in a tall building. There's no garden. They usually drive every day because the city is too large. They can also choose to go by bus. But the streets are busy. At weekends,Joe is very busy. He often reads books in the library and goes to the park. There's a large zoo. He can see many animals with his new friends.
Joe's life in the city is very different from the life in the small town. He sees more(更多的)people. He goes to more places. But some things are the same. He is with his family. He still goes to school and helps his mother do housework.
，已知它的二氯代物有10种，则其六氯代物有( )
