题目

下列区分物质的方法均正确的是（ ）选项要区分的物质方法一方法二A羊毛和锦纶点燃闻气味看颜色B硫酸钾和硝酸铵加水观察加水后滴入氯化钡溶液C二氧化碳和氧气通入氢氧化钠溶液通入紫色石蕊溶液D18K金和黄铜空气中加热加入稀盐酸A.A B.B C.C D.D 答案：【答案】B【解析】A、羊毛和锦纶点燃后有烧焦羽毛味是羊毛，有刺激性气味的锦纶，点燃闻气味可以区分；羊毛和锦纶会有相同的颜色，不能通过观察颜色区分；故选项错误；B、硫酸钾固体溶于水无明显的吸、放热现象，但硝酸铵固体溶于水会吸收热量，可以通过加水区别；硫酸钾能与氯化钡反应产“Any time! Any where! Decades ago there was no such thing” – “Communication”. Then, September 7th 1987, the global system for mobile communication or GSM was born. And international agreements that laid out the standards, regulations and practices gave rise to a global mobile phone industry. To be honest, the world’s first mobiles were not so attractive and the range of effectiveness wasn’t very good. But they became a must-have among those wealthy people who could afford that. However, by advantage of GSM which has many different elements to it, we can all enjoy the ability to go around the world in 217 countries, land in that country and know that a phone would work. There are other cell phone systems using different technology in the world. The majority of the United States and parts of South America have been using something called CDMA which is very rare in Europe. In some Asian countries like China, GSM and CDMA both exist at the same time. But the GSM Association claims 85% of the global mobile phone market. They estimated there are now about 2.5 billion different users who make more than 7 trillion minutes of calls everyday, and that’s not all. 20 years later, the mobile phone is so much more than just a phone. You can use it to send text messages, take pictures, show video, even surf the internet. “The phone itself is involved from just being a communication tool, to be a tool for round-the-clock connectivity, you can not live without it even in a minute.” Mobile consultant Nick Lane also points out with so many customized styles and features, your mobile phone will become a symbol of you. Where will the global mobile phone industry be in another 20 years? Certainly, there will be more connections than better coverage. As for where else technology will take us, one can only imagine. 1. According the passage, we can know that GSM is ____________. A. a global-used mobile phone         B. a global mobile phone industry C. a global mobile phone association    D. a global mobile communication system 2.From this passage, we can infer that ____________. A. as soon as the first mobiles appeared, they became popular and many people have one B. with a GSM mobile phone, you can make a phone call in most parts of the USA C. there are only two cell phone systems in the whole world: GSM and CDMA D. most of the mobile phone users in the world now are using the GSM mobile phone 3. By pointing out “your mobile phone will become a symbol of you”, what does Nick Lane want to tell us about the mobile phone in the future? A. You can have a mobile phone with the unique look and functions as you like. B. Others can find us without any difficulties if we carry our mobile phone. C. The mobile phone can be used as a permit when you enter some places. D. The mobile phone we carry can show others how wealthy we are. 4. What does the writer feel about the GSM development in the following 20 years? A. Satisfied.    B. Worried.    C.Confident     D. Confused.