题干

回答关于微生物的问题.

在植物的生态环境中,存在着各种各样的微生物,它们有的附着于植物表面,有的则生活于植物体内.有资料显示,一些植物内生微生物与宿主发生关联时,可明显增强宿主的抗病性,提高植物的生产力.以下为从菠菜叶中分离内生细菌,筛选出对菠菜枯萎病菌有拮抗作用的菌株的过程.

【步骤一 菠菜叶内生细菌的分裂】



【步骤二 菠菜枯萎病毒拮抗菌株的筛选】


【步骤三 菠菜叶内生细菌种类的鉴定】

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阅读下面短文,从短文后各题所给的A、B、C、D四个选项中,选出最佳选项。

    Do you want to be successful in everything you do? If so, then 1? Here is an example.

    There was a farmer who 2 corn(玉米) all his life. Each year he took his corn to the market. Then each time his corn was chosen as the 3 and won the first prize.

    One year a newspaper reporter interviewed him and learned something 4 about how he grew it. The farmer  5 his seed (做种子的) corn to his neighbours.

    "How can you share your best seed corn with your neighbours?" the reporter asked. "You know they are taking part in the 6 with you each year. "

    "Why, sir," said the farmer, "didn't you know? The 7 picks up pollen (花粉) from the corn and moves it quickly from field to field. If my neighbours grow 8 corn, cross-pollination (异花传粉) will affect the quality of my corn. So if I want to grow good corn, I must   9 my neighbours to grow good corn. "

    The farmer knows much about the connection of life.  His corn cannot improve 10 his neighbours' corn improves.

    As a great man says, "We make a living by what we 11; we make a life by what we give." We can't  12 without food, clothes, and many other things. However, a meaningful life is not decided by how much we can get, 13  by how much we can give others. Giving, instead of taking, makes us 14 from other animals.  So those who choose to live well must help others to live well and those who choose to be happy must help others to find 15 in their life.