阅读下面材料，在空白处填入适当的内容（不多于3个单词）或括号内单词的正确形式。

    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 designed ____ (take) 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 from terrible memories. ____, those who are____ the research say that maybe the pills can change people's memories and changing memories is very ____ (danger) because memories give us our identity.