题干

某实验小组为了探究教室的空气中是否有细菌存在,进行了如下实验:(    )

①准备甲、乙2套装有牛肉汁培养基的培养皿,经高温消毒后备用.

②将2套培养皿同时放在教室内,并将甲培养皿盖打开,5~10分钟后再盖上,乙培养皿盖不打开.

③将2套培养皿同放在温暖的地方培养.

④每天观察一次2套培养皿中所发生的变化,并记录.

请根据以上实验回答下列问题:

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    When I was a baby, I entertained you and made you laugh. Whenever I was “bad”, you'd shake your finger at me and ask, “How could you?”--but then you'd give up, and roll me over for a belly scratch and I believed that life could not be any more perfect.

    My housetraining was a long process, because you were terribly busy, but we worked on that together. We went for long walks, runs in the park and car rides. We stopped for ice cream. I took long naps in the sun waiting for you to come home at the end of the day.

    Gradually, you began spending more time at work and on your career, and more time searching for a human mate. Eventually, you fell in love. She, now your wife, is not a dog person, but I still welcomed her into our home. I was happy because you were happy. Then the human babies came along and I shared your excitement, I was fascinated by their pinkness, how they smelled, and I wanted to mother them too. Your wife was afraid I would bite them. But nevertheless, as they began to grow, I became their friend.

    Now, you have a new job in another city and you and they will be moving to an apartment that does not allow pets. You've made the right decision for your “family”, but there was a time when I was your only family.

    I was excited about the car ride until we arrived at the dog pound. It smelled of dogs and cats, of fear, of hopelessness. You filled out the paperwork and said, “I know you will find a good home for her.” They shrugged and gave you a pained look. The children were in tears as they waved me goodbye. And “How could you?” were the only three words that swept over my mind.

    Is it better to live with hope or without hope? At first, whenever anyone passed my pen (围栏), I rushed to the front, hoping it was you, that you had changed your mind and that this was all a bad dream.

    My beloved master, I will think of you and wait for you forever. I hope you receive more faithfulness from your family than you showed to me.