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问题 问答题 简答题

进行滴定分析，必须具备以下几个条件？

答案

参考答案：共具备三个条件，

（1）要有准确称量物质的分析天平和测量溶液体积的器皿

（2）要有能进行滴定的标准溶液，

（3）要有准确确定理论终点的指示剂

单项选择题

It’s not easy to be an astronaut’s son. Everybody expects you to be special or perfect. I often wonder how my father ever had a son like me. I mean he’s so special and so good at everything he does. Even in middle school he was class president and captain of the football team.
Well, to be honest, I often dream about being some kind of hero or doing something special-like saving a child from a burning building or discovering a new star. I was daydreaming at school one morning when my teacher said there would be a Father’s Day writing competition for the whole school. "I hope we have a winner right here in my class. "
When I got home, I started to think about what to write. My father is an astronaut. No, I wouldn’t start like that. That was the way others saw him. How did I see my father Hmm.
I saw him sitting with me in the dark when I had a terrible dream. I remembered how he hugged me for hours when my dog Spotty was killed by a car. Yes, these were the things I was going to write. To me, he wasn’t just a world-famous astronaut. He was my dad.
My parents and I went to school Thursday night. There were so many people in the big hall! My dad looked at me, and I shrugged (耸肩).
The third prize was announced and it was not me. I was relieved (释然) and disappointed at the same time. The second prize was announced. It was me.
I went up to the stage and read what I had written, My Father’s Son. When I finished, the people stood up and cheered. I saw my father blowing his nose. Tears were running down my mother’s face. Dad cleared his throat and put his hand on my shoulder. "Son, this is the proudest moment of my life. "
It was the proudest moment of my life, too. Maybe I’ll never be a great hero or win a Nobel Prize, but it was enough just to be my father’s son.

The writer felt proud when he ______.

A．got a prize in a writing competition
B．won a Nobel Prize
C．saved a child from a burning building
D．discovered a new star
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单项选择题

当传输一个支付指令时，以下哪一项可用来帮助校验该指令不是被复制的（）。

A.使用密码学的哈希算法

B.加密消息摘要

C.解密消息摘要

D.（使用）序列号及时间戳
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