John has lived in London for a few years, but he isn't so familiar with that city, because he seldom goes out. One foggy morning, he had to go somewhere to attend an important meeting. Because of the heavy fog, he was unable to get the right way. Although he asked many people for the direction, no one paid attention to him, for they were all in a hurry. He looked so anxious. At this very moment, a woman came out of the fog and said, “Let me help you, Sir. Please go with me." John followed the woman, and then she led him to the right place. It took them about half an hour. John owed his great thanks to her. However, to his great surprise, he found that the woman was blind. “How can you take me here?" John asked. “I have been living in London since I was born, so I'm very familiar with every street in this city." the woman answered.