A well-dressed man enforced a famous jewelry shop. He explained that he wished to buy a pearl for his wife's birthday. The price didn't matter. Since business had been very good for him that year. After examining a nice black one that cost $5000, he paid for the pearl in cash, shook hands with the jeweler, and left.　　A few days later the man returned and said that his wife liked the pear so much that she wanted another one just like it. It had to be exactly the same size and quality. "Can you give me any advice on how to get such a pearl?",said the man. The jeweler regretfully replied, "I would say it's exactly impossible to find one exactly like that pearl. The rich man insisted that the jeweler advertise in the newspapers, offering $ 25,000 for the matching pearl. Many people answered the advertisement but nobody had a pearl that was just right.　　Just when the jeweler had given up hope, a little old lady came into his store. To his great surprise, she pulled the perfect pearl from her purse. "I don't like to part with it." she said sadly, "I inherited it from my mother, and my mother inherited it from hers. But I really need the money." The jeweler was quick to pay her before she changed her mind. Then he called the rich man's hotel to tell him the good news. The man, however, was nowhere to be found.3. He told the jeweler to get him another pearl that must be ______.