阅读短文、完成下列小题。

      One midnight, a little girl woke up to pass water. She by herself got up and down her bed, walked to the bedroom door and opened it. She looked outside and walked back, for it was so dark in the hall that she feared.
      Her mother said, "Don't be afraid, honey. Take courage!" "What's courage?" she asked, running to her mother's bed. "Courage is the brave breath," her mother answered. "Mum, do you have courage?"“Certainly." The girl held out her little hands, saying, "Mum, blow some of your breath of courage to me."
      After her mother blew out two mouthfuls of breath into her little cold hands, the little girl clenched her fists(握拳) nervously, afraid that the  "breath of courage” would run away. Then with her fists clenched, she walked out of the bedroom towards the bathroom with nothing to fear.
      Her mother said to herself, "It will be nice if someone can blow some kind of ‘breath’ to me. Then I can hold it in my hands too when I feel terrified or lost."
      In fact, mostly, what we are terrified of is nothing but the fear in our mind. Who we should defeat(战胜) is nobody but ourselves.

实验Ⅰ：称量镁条，在空气中点燃，待反应结束后，将生成物全部收回再称量．

实验Ⅱ：将装有稀盐酸的小试管放入装有锌粒的烧杯中，称量，然后将盐酸与锌粒接触，过一会在称量。

实验Ⅲ：将装有氢氧化钠溶液的试管放入盛有硫酸铜的锥形瓶中，并在锥型瓶口塞上橡皮塞，称量，然后设法将两种溶液接触（有蓝色氢氧化铜沉淀和硫酸钠生成）过一会再称量。数据见下表：