题干

某气态的烷烃与烯烃的混合气体9 g,其密度为同状况下H2密度的11.25倍,将混合气体通过足量的溴水,溴水增重4.2 g,则原混合气体的组成为(  )

A:甲烷,乙烯

B:乙烷,乙烯

C:甲烷,丙烯

D:甲烷,丁烯

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答案(点此获取答案解析)

C

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    I never thought I'd be a “runner”. I was the girl who 1 slowest in the PE class. A few years ago, I was walking with a group of2 in the Race for the Cure, a 5KM race designed to 3 money for the fight against breast cancer4 one lady caught my 5.

    She was one of the weakest-looking women I've ever seen. She must have been close to seventy years old,6a T-shirt with the word “Survivor.” She was so small that it seemed as if she could even be  7by a swift wind. But she was running. And she was 8 me my group of friends. She ran slowly, but 9—as if each step pushed her cancer further into her past. Right at that moment, I 10that in the next Race for the Cure, I'd be running along with her.

    A week later, I found myself in the11, running on the treadmill (跑步机). Three minutes after I started, my face was bright red. I felt like my lungs were going to12. I had to slow down to a walk. I thought of the 13at the race. I kept it up. I was able to go a little  14 each time. Three and a half minutes. Four minutes. Five.

    A year later, I was 15 at the Race for the Cure, but this time, I 16 with the runners. When the race started, the other runners passed me by. I ran forward. I wondered if I'd be 17 to do it. But then, I remembered the brave woman. I ran as fast as I could until I finally crossed that finish line. I had just 18 my first race! I looked down at my legs, 19. They had done something I'd never thought 20. I have never felt stronger than at that moment. And, I knew that I wanted to do it again.