Not all memories are sweet. Some people spend all their lives trying to forget bad experiences.

   Now American researchers think they are close to developing a pill, ____ will help people forget bad memories. The pill is ____(design)to be taken immediately after a frightening experience. They hope it might reduce, or ____(possible) erase (抹去) the effect of painful memories.

   In November, experts tested a drug on people in the U.S. and France. The drug stops the body from ____(release) chemicals that fix memories in the brain. So far, the research ____(suggest) that only the emotional effects of memories may be reduced, not that memories are wiped out. They are not sure to the degree people's memories are affected.

   The research has caused a great deal of ____(argue). Some think it is ____bad idea, while others support it. Supporters say it could lead to pills which prevent or treat soldiers' troubling memories after war. They say that there are many people who suffer ____terrible memories. ____, those who are against the research say that maybe the pills can change people's memories and changing memories is very ____(danger) because memories give us our identity.

当A、B两点中有一点在原点时，不妨设点A在原点，

如图1，|AB|=|OB|=|b|=|a﹣b|；

当A、B两点都不在原点时，

如图2，点A、B都在原点的右边

|AB|=|OB|﹣|OA|=|b|﹣|a|=b﹣a=|a﹣b|；

如图3，点A、B都在原点的左边，

|AB|=|OB|﹣|OA|=|b|﹣|a|=﹣b﹣（﹣a）=|a﹣b|；

如图4，点A、B在原点的两边，

|AB|=|OB|+|OA|=|a|+|b|=a+（﹣b）=|a﹣b|；

回答下列问题：

临近中考，初三（1）班的王磊感到越来越烦躁，动不动就发火：做不完的作业，背不完的书，政治历史今年也要闭卷考试，我最怕背，语文英语是我的薄弱学科，上次周练考得很不理想，长跑肯定不达标……后来，通过听听音乐，打打篮球，不快的情绪慢慢就消散了。对此认识正确的是（   ）

— ______. I have to do my homework.