阅读对话，用所给词的适当形式填空。

Maria: Hello, Ben!

Ben: Hello, Maria! How are you?

Maria: Fine. ____ And you?

Ben: I'm OK. Excuse me, do you ____ a sister?

Maria: Yes. ____ name is Beth. She is eight ____ old.

Ben: Does she have a ____ nose?

Maria: Yes. But her mouth is wide.

Ben: Can you help me to know her?

Maria: OK.

    We each have a memory（记忆力）. That's why we can still remember things after a long time. Some people have very good memories and they can easily learn many things in a short time, but some people can only remember things when they say or do them again and again. Many of the great men of the world have got surprising memories.

    A good memory is a great help in learning a language. Everybody learns his mother language when he is a small child. He hears the sounds, remembers them and then he learns to speak. Some children are living with their parents in foreign countries. They can learn two languages as easily as one because they hear, remember and speak two languages every day. In school it is not so easy to learn a foreign language because the students have so little time for it, and they are busy with other subjects, too.

    But your memory will become better and better when you do more and more exercises.

什么是热岛效应？产生的原因是什么？