示例:
There is a businessman in the town. He sells pearls. To attract customers, he uses beautiful boxes to pack the pearls.
One day, a customer comes to the shop. The businessman shows his beautiful pearls to the customer. The customer likes the box with a nice pearl in it so much. He pays a lot of money for it. And the businessman is very happy that someone likes his pearl. However, to his surprise, the customer comes back. He returns the pearl to the businessman.
