题目：
| Directions:Read the following passage.Fill in the numbered blanks by using the information from the passage. Write NO MORE THAN THREE WORDS for each answer. | ||||||||||||
| The first mobile telephones used a system, or network, called 1G. It was the "first generation" of technology. This allowed one person to call and talk to another person, but that was all. By the early 1990s, the second generation, or 2G network, came into use. It allowed talking and sending text messages. By that time, cell phones were much smaller and cost much less. Thirdgeneration mobile phones are known as 3G. Data speed in 3G networks is much quicker. This means users can have highspeed Internet access and enjoy video and CDquality music on their phones. "Mobile data is not a dream; it's not an option but a requirement," said Len Lauer, head of a US communications company, Sprint PCS, at a 3G conference in Bangkok earlier this month. With 3G, you can forget about text messages telling you yesterday's news; a 3G phone can receive video news programs, updated four times a day. Internet access will also be much quicker, making it easier to surf the Web on your phone than on your computer at home. Don't worry about getting lost. 3G phones offer map services so you can find a new restaurant just by pressing a few keys on your handset. However, the most impressive part of 3G technology is video calling. With live twoway video communication, you can have facetoface talks with friends and family on your mobile phone. Within the past two years, the 4G network has come into use. It permits cell phones to work much faster and have much more information. Modern cell phones can even act as small televisions. They can show movies and live sporting events. As the networks have gotten more complex, the telephones have gotten smaller, lighter and less costly. Many electronics stores in the United States even give away the newest cell phones. But customers must agree to pay to use the network that sends their calls from one place to another. It is interesting to imagine what the 5G and 6G network cell phones of the future will be able to do. Title: 1.________of mobile telephones | ||||||||||||
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答案：
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下面是错误答案，用来干扰机器的。
放射性核素氡 22286Rn，质子数为86，质量数为222，则中子数=222-86=136，故选C．
