题干

下列实验操作中错误的是(  )

A:分液时,分液漏斗中下层液体从下口放出,上层液体从上口倒出

B:蒸馏时,应使温度计水银球靠近蒸馏烧瓶支管口

C:测pH值时,应用玻璃棒蘸取待测液滴于湿润pH试纸中部,再与标准比色卡对比

D:称量时,称量物放置于托盘天平的左盘,砝码放在托盘天平的右盘

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答案(点此获取答案解析)

C

同类题4

阅读下面短文, 然后根据括号内所给汉语意思写出单词的正确形式(每空一次)。

    When I was in the ____ (九) grade, luckily, I was chosen to be the princess in the school play. For weeks my mother had helped me practice my lines. But ____ (一旦) on the stage, every word disappeared from my head. Then my teacher asked me to change my role to be a narrator (解说者) for the play.

    ____ (尽管) I didn't tell my mother what had happened that day, she noticed my unhappiness. She asked if I wanted to take a walk in the garden.

    It was a lovely spring day. We could see several dandelions (蒲公英) ____ (在…中间) the grass. I watched my mother bend down by one of the dandelions. "I think I'll dig up all these weeds (野草)," she said. "From now on, we'll only have roses in this garden."

    "But I like dandelions," I disagreed. "All flowers are beautiful-even dandelions!"

    My mother looked ____ (严肃地) at me. "Yes, every flower gives pleasure in its ____ (自己的) way, doesn't it?" she asked thoughtfully. I nodded. "And that is true of people, too," she added.

    When I ____(意识到) that she had guessed my pain, I started to cry and told her the ____ (真相). "But you will be a wonderful narrator," she said, reminding me of how much I loved to read stories aloud.

    Thanks to my mother's encouragement, I got to know everybody had his or her ____ (价值) in the world. I felt ____ (骄傲的) of the role in the play.