生长素的运输方向是单向的，一般只能从植物形态学的上端向形态学的下端运输，而不能反过来运输，这最可能是由于       （  ）

温家宝总理在国务院常务会议上强调,切实向民营资本开放法律法规未禁止进入的行业和领域，鼓励民营资本通过兼并重组等方式进入垄断行业的竞争性业务领域。鼓励民营资本进入垄断行业 
①有利于促进非公有制经济的发展 
②有利于消除企业之间的非法垄断和不正当竞争
③有利于社会资源的合理配置和有效利用 
④有利于促进我国经济又好又快发展

一位诗人在公园里散步，在一条只能一个人通过的小路上，与对面走过来的评论家相遇。这个对诗人有成见的评论家说：“我从来不给蠢货让路。”“我恰恰相反。”诗人说完，笑着退到了路边。下列说法，你不同意（）

阅读下列短文，从每题所给的四个选项（A、B、C和D）中选出最佳选项。
      When an animal helps another animal，it usually gets something valuable in return. For a long time，many scientists thought that only people could act generously just because it feels good.
      However，a new study in Germany suggests that chimpanzees (an animal like a large monkey without a tail ) also do good things for no real reason. And so do children who are as young as 18 months of age. Maybe it is because humans and chimpanzees share an ancestor about 6million years ago.
      People and chimpanzees appear to develop such features without any other training，says Warneken，a scientist in Germany.
      Warneken and his partners worked on adult chimpanzees that live on an island in the African country of Uganda. They also worked with 18-month-old children in Germany. The researchers performed three experiments on the adult chimpanzees and two experiments on the kids. In the first animal experiment，a person tried to reach his arm into a cage to get a stick，but he couldn't reach it. A chimpanzee was in the cage，and it could reach the stick if it wanted to.
      Thirty-six chimpanzees took part in this experiment one by one，and no chimpanzee saw what the other chimpanzees had done. Even though the animals hadn’t met the person before，they usually took the stick and gave it to the person. What's more，they did this whether or not the person offered them bananas as a reward.
      In a similar experiment，36 children acted in a similar way. They helped the person reach the stick，whether or not they were offered toys for their help.
      Researchers did other experiments on chimpanzees and babies. No rewards were offered in either experiment. And still，both the chimpanzees and children went out of their way to help. Still，the new study is different from earlier findings. Researchers have found that chimpanzees don't give rewards of food to other chimpanzees，even if it costs them nothing to be generous.

一个物体在另一个物体上滑动时的摩擦叫做____，除了此摩擦外，还有____和____．