题干

某兴趣小组为探究铝镁合金的组成,取16g铝镁合金样品,将60g氢氧化钠溶液平均分成三份依次加入样品中(镁与氢氧化钠溶液不反应,铝与氢氧化钠溶液反应的化学方程式为:2Al+2NaOH+2H2O═2NaAlO2+3H2↑),充分反应后,过滤出固体,将其洗涤、干燥、称量,得实验数据如下:计算:

 所加氢氧化钠溶液的次数

 第一次

 第二次

 第三次

 所加氢氧化钠溶液的质量/g

 20

 20

 20

 剩余固体的质量/g

 10.6

 5.2

 4.0

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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。

A

     I am a taxi driver. One Monday morning, I had stopped at New York Hospital when I found a well-dressed man coming over. He was waving to me. I waited until he jumped into the cab. “La Guardia Airport, please,” he said.

     As always, I wondered about my passenger. “What do you do?” “I am working at the hospital.” For some unknown reason, I decided to ask for his help.

     “Could I ask a favor of you?” He didn’t answer. “I have a son, 16. He’s doing well in school. He wants a job this summer. Is there any possibility that you might get him a summer job?” After a minute, he said, “The medical students have a research project. Maybe he could fit in. Have him send me his school records.” He searched his pocket and handed me a card.

     That evening, I pulled the card from my pocket. “Robbie,” I said proudly, “This could be a summer job for you. Send him your school records.” He read it out loud, “Fred Plum, New York Hospital.” “Is this a joke?” he said in doubt. After I shouted and threatened (恐吓) to cut off his pocket-money, Robbie promised to send off his grades the next morning.

     Two weeks later, when I arrived home, my son handed me a letter from Plum. He was to phone Plum’s secretary for an interview.

     Robbie got the job. The white coat he wore made him feel more important than he really was. As high school graduation neared, Plum was kind enough to write letters of recommendation (推荐) for universities. At last, Robbie was admitted to New York Medical College.

     It never happened to me that a stranger should change my son’s future.