题目

完形填空 Mastery of a language is one of the greatest 1 that one can ever have. Many people have a passion (激情) for learning languages. Human language evolve (进化) from hand gestures and other signs that people used to 2with each other. Ancient people started with drawing3about what they wanted to say, which later on evolved into some languages, after which many other dialects (方言) have come into 4. With over 2,700 different languages and 7,000 dialects5 all over the world, the world has many different cultures that6 speak their native dialects. One such 7 that is even older tha某溶液含有①NO、②HCO、③SO、④CO、⑤SO等五种阴离子。向其中加入少量的Na2O2固体后，溶液中离子浓度基本保持不变的是（设溶液体积无变化） A．①    B．①②④     C．①③⑤      D．①③④⑤