下图中甲图表示用某种杆菌为饲料培养大草履虫和双小核草履虫的种群数量变化，其中实线

     Young people are often unhappy when they're with their parents. They say that their parents don't 
  1    them. They often think their parents are too strict with them.    2    often find it difficult to win
their children's trust (信任). They seem to forget how they themselves felt when they were     3   , so
they can't quite understand young people now.    
     For example, young people like to do things without much thinking. It's one of their ways to    4    
that they have grown up and they can do    5    any difficult things. And    6    people worry more easily.
Most of them usually    7    what they will do carefully, while young people don' t.
     Young people often make their parents angry by clothes they    8    , the music they enjoy and
something else. But they don't mean to cause any trouble.    9    just feel that in this way they can be
far away from the old people's    10    and they want to make a new culture of their own. And    11    
their parents don't like their music or clothes or their way of speaking, the young people feel very  
    12   , because sometimes they even don't want their parents to say "Yes" to what they do. They
    13    to stay at home alone and do    14    they like.
      I think young people should try to    15    their parents to understand them. If so, they can get on
well with each other.