问题
填空题
我们知道，石灰水中的氢氧化钙可与空气中二氧化碳反应，生成碳酸钙沉淀。用石灰水涂刷墙壁，就是利用了石灰水的这一性质。使得墙壁越来越硬。实验室配制的一瓶澄清石灰水，敞口放置一段时间后，发现表面有一层白色物质生成，说明空气中含有_____________气体。
答案
二氧化碳
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我们知道，石灰水中的氢氧化钙可与空气中二氧化碳反应，生成碳酸钙沉淀。用石灰水涂刷墙壁，就是利用了石灰水的这一性质。使得墙壁越来越硬。实验室配制的一瓶澄清石灰水，敞口放置一段时间后，发现表面有一层白色物质生成，说明空气中含有_____________气体。
二氧化碳
I live in a big city with a lot of homeless(无家可归的) people. Luckily there’re small ways of helping them and you needn’t have a lot of 31 . One way to help is to buy their monthly magazine. By doing this one day, I got to 32 a young homeless man. He was often 33 the magazine at the train station. He was a poor farmer from another country. After a while, I discovered that his 34 was close to mine. It 35__ that we were born in the same month. I met him last year shortly 36 his birthday, and after congratulating(祝贺) him, without thinking, I asked if he had had a good day. He 37 and said that he hadn’t really celebrated(庆祝). I felt so 38__. I just couldn’t help(情不自禁) thinking of this nice, young man being 39 on his 25th birthday with no presents, no cake, nothing! So I went home and looked in my yarn(毛线) basket. 40 for me, I had enough yarn left. I set to work and knitted(编织) a 41 for the young man. The yarn had become a little dirty 42 I didn’t knit very often. Then I washed the yarn so the scarf(围巾) would be clean when he got it. I met him on my own birthday as I was going shopping. I had 43 to meet him so I had carried the scarf and a piece of my own birthday 44 around with me. He was very happy with these gifts and so was I. The 45 in his eyes was the best present he could have given me!
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