李明同学放学回家，正碰上刮风下雨，他以18km／h的速度由西向东快跑．此时他发现了奇怪的现象：雨滴呈竖直下落状态．请你确定：这时刮的是____ 风，风速是____  m/s。

创新与开放，促进发展和进步，保守与封闭，导致停滞和落后。

【制度创新】

秦汉时期，为加强中央集权和防止官员贪腐开创了监察制度并不断加以强化。

【对外交流】

西汉以来，一条横贯欧亚大陆的通道上，五彩的丝绸、精美的瓷器和名贵的香料贸易络绎不绝。这条通道为古代东西方之间经济、文化交流做出了重要贡献。　　

【封闭落后】

乾隆二十二年（1757年），清政府规定广州是允许外商来华贸易的唯一口岸，而且即使在广州也百般限制中国人与外商接触。政府特许的“十三行”不仅垄断了与外商的经济往来，还代政府出面办理交涉事宜。

阅读短文，根据短文内容及首字母提示，在空白处填入一个适当的单词。
      Think about two people you know. How would you describe their personalities? Are they the  s ____  ?Of course not! Everyone is different .Even twins have  d ____ personalities.
    Some people are very outgoing and  f____  .They like to be  w____  other people all the time. And some people are quiet, maybe even shy. They like to be alone or play with a  f____   friends.
    Some people worry a lot. They may  w ____ about many things.  H____ ,some people don't worry about anything! They  n____ mind what is going on next. These people are very relaxed.
    Some people are h____ .They always do their best. They aren't lazy. They always get more chances to have success.
And don't  f ____  this: Everyone is different. That means you are special.

计算：$\frac{4}{x^2-4}$﹣$\frac{1}{x-2}$的正确结果是（　　）