下列反应现象“先变红后褪色”的是
A．SO2与紫色石蕊溶液
B．过量的Cl2与KI淀粉溶液
C．硫化氢与醋酸铅试纸
D．Na2O2与酚酞溶液
答案：D
题目分析：A中SO2与紫色石蕊溶液只变红。 B中过量的Cl2与KI淀粉溶液发生反应生成了碘单质，碘与淀粉变成了蓝色。C中硫化氢与醋酸铅试纸出现黑色。 D中Na2O2与酚酞溶液时，过氧化钠先和水反应生成过氧化氢和氢氧化钠，溶液呈碱性溶液变红，但过氧化氢有漂白性，红色又褪去。
| I could have easily gone through life without getting to know one of the most romantic feelings－love for a dog. For at least years my 1 had been suggesting that we get a dog. There were several reasons why the idea came up. We had noticed that, on our block, couples with no children as a rule 2 one large or two small dogs. So we got one puppy since we had no children, either. He flew into the house at high 3 . In several minutes he ran over all the house, jumped from my shoulder onto the bed, and ended up in the 4 , where my wife washed him with motherly 5 . From that day on, the invisible(看不见的) war for the love of my new member of our family began at my home. He seemed to 6 that at once. Most of the meals that my wife had 7__ for him with greater care than those for me－he didn't even look at. Every evening I went out walking with him. I could not know who was walking whom until one evening, when, tired from work, I _8 the walk. The dog was very angry and dragged me out. Last night our dog pulled me by the ear with his teeth, 9 me up in my dream, and dragged me into the kitchen to make me turn off the __10 which had disturbed his sleep. I meekly(乖乖地) admited that I had forgotten to switch off the light, but that was not _11 . He looked at me like a teacher at a pupil who repeatedly makes mistakes. Now we finally know who's the 12 _ at home, and for twenty years we had seriously argued whether it was my wife or I. | ||||
|