A man once had a dream about the Black Forest in Germany. In his dream he was walking in the forest when two men ran out and tried to throw him to the ground. He ran off as fast as he could,but they followed him. He reached a place where he saw two road in front of him,one to the right and the other to the left. Which road should he take?He heard the two men behind him, getting nearer, and at the same time he heard a voice in his ear. It told him to go to the right,and he did so. He ran on and soon came to a small hotel. He was received there kindly and given a room,and he was saved from the two men. That was the dream.
Twenty years later he was really in the Black Forest and , as happened in the dream long ago, two men ran out and tried to throw him down. He ran off, and came to a place with two roads, like in the dreams. He remembered the dream and took the road to the right. He soon reached a small hotel , was taken in, and so was safe. His dream of twenty years before had saved his life.
的离心率是（ ）