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问题 选择题

下列反应既是氧化还原反应又是离子反应的是    

A．碳在二氧化硅反应

B．二氧化碳通入澄清石灰水中

C．氯化钠溶液中滴加硝酸银溶液

D．锌粒投入稀硫酸中

答案

答案：D

反应中元素的化合价发生变化的是氧化还原反应，有离子参加反应的是离子反应，A是氧化还原反应但不是离子反应；D二者都是；B、C只是离子反应，D正确。

问答题

Internet is a vast network of computers that connects many of the world’s businesses, institutions, and individuals. (46) The Internet, which means interconnected network of networks, links tens of thousands of smaller computer networks. These networks transmit huge amounts of information in the form of words, images, and sounds.
The Internet has information on every topic.(47)Network users can search through sources ranging from vast databases to small electronic" bulletin boards", where users form discussion groups around common interests. Much of the Internet’s traffic consists of messages sent from one computer user to another. These messages are called electronic mail or e-mail. Internet users have electronic addresses that allow them to send and receive e-mail. Other uses of the network include obtaining news, joining electronic debates, and playing electronic games.(48)One feature of the Internet, known as the World Wide Web, provides graphics, audio, and video to enhance the information in its documents. These documents cover a vast number of topics.
People usually access the Internet with a device called a modem. Modems connect computers to the network through telephone lines. Much of the Internet operates through worldwide telephone networks of fiber-optic cables(49) These cables contain hair-thin strands of glass that carry data as pulses of light. They can transmit thousands of times more data than local phone lines, most of which consist of copper wires.
In the future, the internet will probably grow more sophisticated as computer technology becomes more powerful. (50)Many experts believe the Internet may become part of a larger network called the information superhighway. This network, still under development, would link computers with telephone companies, cable television stations, and other communication systems. People could bank, shop, watch TV, and perform many other activities through the network.
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单项选择题

中国健美操协会是中国奥委会承认的全国性运动协会，它成立于（）年。

A.1987

B.1992

C.1997
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