下列物质中，属于纯净物的是（ ）
A．
结晶粗盐
B．
新鲜空气
C．
不锈钢
D．
干冰
A、粗盐的主要成分是氯化钠，还含有泥土、氯化钙等物质，属于混合物．故选项错误；
B、空气中含有氧气、氮气、二氧化碳等物质，属于混合物．故选项错误；
C、不锈钢的主要成分是铁，还含有碳等物质，属于混合物．故选项错误；
D、干冰中含有一种物质二氧化碳，属于纯净物．故选项正确．
故选D．
阅读下面短文， 从短文后所给的四个选项（A、B、C、D）中，选出可以填入空白处的最佳选项。 Recently I understood the true meaning of love. That would have been, Kane, a boy. Kane was the two-year-old son of Joline, my new neighbor, who moved here from California. Kane was born with hard sticks for . And on that morning I the effect that Kane’s physical had on his family. But I also witnessed so much that. I saw an extraordinary family that embraced this special child, a family that wouldn't allow Kane to know he was . Joline had constructed a small cart just a few inches the floor for his son to get around. Using his hands to move about, the cart Kane to “go to” any place just as else was able to do. Kane was more than just a member of the family, he was the . Much later in my life, I came to that God had sent this child to help some of us who just weren’t getting what was all about. Even with my limited capacity for understanding at that time I knew that Kane was a developed spirit with great wisdom. Kane demanded attention, not because of his mobility challenges or other apparent shortcomings. In his mind, he had no or shortcomings. The truth is that he received because he was alive and real and had so much to offer. Kane was and is lots of warm and powerful energy to us all so we might learn that ： Love surpasses all things. If you met this kid, you’d want him for a friend he was with so much to .
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