题干

将a组小麦培养于含18O的CO2的空气中,将b组小麦培养于含18O的O2的空气中,正常生长一段时间,a、b两组最先出现放射性氧的化合物依次是          (  )

C:五碳化合物和水

A:葡萄糖和二氧化碳

B:三碳化合物和水

D:三碳化合物和丙酮酸

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答案(点此获取答案解析)

B

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    I was feeling really down because my long-time friend had died. Then I started a six-week volunteering at a nursing home all day even Saturday. My duty was to serve the meal and clean up. One day I was told to go to Room 117 to make sure the patient was all right. I found a boy of eight sitting in bis bed watching a movie. I was shocked to see a child in this seemingly forgotten nursing home for the old. He was so small and weak that you had to look closely to find him. I grabbed his medical chart and found out :he had a terminal(绝症的) illness.

    We started to talk, and I found out that his family rarely visited, and all he did every day was watching TV I wanted to cry for him, and for my lost friend. As we talked, he had a smile on his face, and I asked him why and how he still managed to stay happy.

    He thought for a moment, and then said that too many people were dead even before they died. They walked around feeling that God had cursed(诅咒) them and they had nothing to live for.

    The boy said that he would not be like that. He woke 'every morning thankful to see another sunrise. He kept his window open so that he could smell the flowers and feel the heat of the sun. He also said that he had hope.

    "Too many people haven't seen much of that around here." He said, "Life is full of hope and we need to live life before it is gone."

    I don't know what happened to him. I guess he passed away, but his lesson lives on. I now wake up and live each day to the fullest. The key to life is not money or fame, but the lesson we learned from it.