A famous teacher was speaking to the students at our school. He began his lesson by holding up a ￥100 bill. Then he said to the three hundred students,“Who would like this ￥100 bill?” The students began to put up their hands at once.
    Then he said,“I am going to give this ￥100 to one of you, but first, let me do this.” He then made the bill into a ball. Then he said, “Who wants it now?” The hands went back into the air.
  “Well,” he said,“What if I do this?” and he dropped it on the floor and stepped on it. He picked up the dirty, crumpled bill and said, “Who still wants it？” Hands went back into the air.
  “My friends,” he said, “you have learned a valua-ble lesson today. No matter  what I did to the money, you still wanted it because it did not go down in value （价值）. It was still worth ￥ l00!”
    Many times in our lives, we are dropped, crum-pled, and stepped on by the chances we take and the things that happen to us. We feel as if we are worth nothing. But remember, no matter what has happened to you, you will never lose your value: you are always valuable to those people who love you. Your value doesn't come from what you do or whom you know, but WHO YOU ARE.
You are special and valuable. Don't ever forget it!

已知$\frac{\sin a-2\cos a}{3\sin a+5\cos a}=-5$,则tana=（    ）

法国数学家、物理学家、哲学家和散文大师帕斯卡曾说过：“人只不过是一根苇草，是自然里脆弱的东西；但他是一根能思想的苇草。……我们额全部尊严就在于思想。”这段的意思是（   ）