关于家鸽的气囊叙述不正确的是（） A．分布在内脏器官之间 B．有的气囊突入到骨的

读“非洲主要气候类型”图，非洲分布面积最大的气候类型是

A．热带雨林气候　

B．热带草原气候

C．热带沙漠气候　

D．热带季风气候

瓶颈产业往往属于基础产业，是“上游”产业，制约其他产业发展，而受其他产业影响小，其特点有()。

A.建设投资额较低，投资回收期短

B.建设投资额高，投资回收周期长，风险大

C.价格弹性小，对市场数量信号反映不灵敏

D.资本流动性差

E.资本流动性良好

配管经过伸缩缝时，应加（）、补偿装置。

A、接线盒

B、固定卡

C、接地线

D、护套

TEXT C
In April 1995, a young Chinese chemistry student at Beijing University lay dying in a Beijing hospital. She was in a coma, and although her doctors had performed numerous tests, they could not discover what was killing her. In desperation, a student friend posted an SOS describing her symptoms to several medical bulletin boards and mailing lists on the Internet. Around the world, doctors who regularly checked these electronic bulletin boards and lists responded immediately.
In Washington D. C. , Do, John Aldis, a physician with the U.S. Department of State, saw the message from China. Using the Internet, he forwarded the message to colleagues in America. Soon an international group of doctors joined the e- mail discussion. A diagnosis emerged -- the woman might have been poisoned with thallium, a metal resembling lead. A Beijing laboratory confirmed this diagnosis -- the thallium concentration in her body was an much as 1,000 times normal. More e-mail communication followed, as treatment was suggested and then adjusted. The woman slowly began to recover. Well over a year later, the international medical community was still keeping tabs on her condition through the electronic medium that saved her life.
It’s 11: 30 p. m. , you’re is San Francisco on business, and you want to check for messages at your office in Virginia. First you dial in and get your voice mail. Next you plug your portable computer into the hotel-room telephone jack, hit a few keys, and pick up e-mall from a potential client in South Africa, your sister in London, and a business associate in Detroit. Before writing your response, you do a quick bit of search on the Internet, tracking down the name of the online news group you had mentioned to the man in Detroit and the title of a book you wanted to recommend to your sister. A few more keystrokes and in moments your electronic letters have reached London and Detroit. Then, knowing that the time difference means the next workday has begun in South Africa, you call there without a second thought.
These stories reflect society’s increasing reliance on system of global communication that can link you equally easily with someone in the next town or halfway around the world. The expanded telephone-line capacity that has allowed the growth of these forms of communication is a recent phenomenon. The United States has enjoyed domestic telephone service for more than a century, but overseas telephone calls were difficult until relatively recently. For a number of years after World War Ⅱ, calls to Europe or Asia retied on short-wave radio signals. It sometimes took an operator hours to set up a 3- minute call , and if you got through, the connection was often noisy.
In 1956, the first transatlantic copper wire cable allowed simultaneous transmission of 36 telephone conversations -- a cause for celebration then, a small number today. Other cables followed; by the early 1960s, overseas telephone calls had reached 5 million per year. Then came satellite communication in the middle 1960s, and by 1980, the telephone system carried some 200 million overseas calls per year. But as demands on the telecommunication system continued to increase, the limitations of current technology became apparent. Then, in 1988, the first transatlantic fiber-optic cable was laid, and the "information superhighway" was on its way to becoming reality.
Optical fibers form the backbone of the global telecommunication system per, length for length, than steel -- were designed to carry the vast amounts of data that can be transmitted via a relatively new form of light-tightly focused laser. Together, lasers and optical fibers have dramatically increased the capacity of the international telephone system. A typical fiber-optic cable made up of 100 or more such fibers can carry more than 40,000 voice channels. With equally striking improvements in computing, the new communication technology has fueled the exponential growth of the phenomenon known as the Internet.

The highly efficient modem communication system began ______.

A．over a century ago

B．in the middle 1960s

C．in the late 1980s

D．in the year 1980

单层套管头（表层套管头）只安装单只套管头的井一般为低压浅层生产井，（）。

A、高含硫油气井

B、含硫油气井

C、相对井控风险较大

D、相对井控风险较小