Bob was a homeless boy who lived in a house for homeless children. He always felt lonely and sad. He felt he was a nobody in this world. One day, he said to Mr. White, head of the house, "Why did my parents bring me to this world? What value do I have now?" Mr. White gave Bob a stone and said to him, "Take it to the market, but don't sell it no matter how much money they pay you. Bob took the stone to a market called Green Market. A man wanted to buy it for 100 pounds, and Bob wouldn't sell it. Later, another buyer would pay more for the stone, but Bob still wouldn't sell it. The next day in Center Market, the people would buy it at a much higher price. But Bob wouldn't sell it. The third day, Bob took the stone to Street Market. This time, the people there offered a price which was ten times higher than that in Green Market. But Bob wouldn't sell it. Bob couldn't understand. He asked Mr. White, " Why did they pay me so much money for just a stone?" " Even for a stone, if you think it valuable, it will be valuable, " said Mr. White. ,. What is the best title for this passage?
A homeless boy A valuable lesson An expensive stone A house for children