Once upon a time a man became a great archer(射手).He asked the king to declare him as the greatest archer of the country. The king was about to do so when an old servant of the king said，“Wait，sir.I know an old man who lives in the forest. He is a much greater archer. Let this young man go to him and learn from him for at least three years.”
   The man could not believe that there could be a greater archer than him，but he went and found the old man and he was! For three years he learned from him.Then one day，when he thought he had learned everything，the thought arose in him：“If I kill this old man，then I will be the greatest archer.”
   The old man had gone to cut wood and he was coming back carrying wood on his shoulder. The young man hid behind a tree,waiting to kill him. He shot an arrow(箭). The old man took a small piece of wood and threw it.It struck the arrow and the arrow turned back and wounded the young man.The old man came，took out the arrow and said.“I knew that some day or other you were going to do this. That's why I have not taught you this secret. There is no need to kill me. My master is still alive,and I'm nothing before him. You must be with him for at least thirty years. And he is very old，So go fast! Find the old man!”

祖国大陆获得统一，各族人民实现了大团结的标志是（    ）

萍萍是位音乐爱好者，钢琴独奏或手风琴独奏她一听便能分辨，她的区分依据是这两种乐器发出声音的 ____不同；她用不同的力弹琴时，发出声音的 ____不同．