下列实验操作正确的是 A.在2mL10%的氢氧化钠溶液中滴入2%的硫酸铜溶液4~

题型:选择题

问题:

下列实验操作正确的是

A.在2mL10%的氢氧化钠溶液中滴入2%的硫酸铜溶液4~6滴,配制新制氢氧化铜悬浊液,检验醛基

B.实验室制乙烯时,迅速升温到140℃

C.用乙醇和浓硫酸除去乙酸乙酯中混有的少量乙酸

D.用苯、2mol/L的硝酸和3mol/L的硫酸制硝基苯

考点:炔烃的通性烷烃的通性烯烃的通性芳香烃的通式
题型:选择题

△+□=100,△×□的积最大是[ ]

A.10000

B.99

C.2500

D.无法确定

题型:选择题

不属于气候形成因素的是()。

A、辐射

B、大气环流

C、气旋

D、下垫面

题型:选择题

肾上腺皮质腺瘤的描述哪一项是正确的:

A.多为双侧

B.直径较小,1cm——2cm 多见

C.肿瘤形态常不规则

D.肿瘤多呈强回声

E.边界不清

题型:选择题

打开一个数据库的命令是______。

A.USE

B.USE DATABASE

C.OPEN

D.OPEN DATABASE

题型:选择题

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.

(48)One feature of the Internet, known as the World Wide Web, provides graphics, audio, and video to enhance the information in its documents.

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