示例:
There were three pigs in the forest. They were brothers and lived with their mother. The house was too small,so they decided to build a house on their own.They bought a lot of bricks and wanted to make a house with bricks. They thought this kind of house was strong. One day, a wolf wanted to eat the three pigs. But the three pigs ran quickly into the house and played a trick on the wolf.The wolf got very angry, but he couldn't go into the house to catch them. At last,the wolf had to go away with nothing. How clever the three pigs were !
