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问题 单项选择题

关于Linux说法正确的是______。

A．Linux操作系统与Windows NT、NetWare、UNIX等传统网络操作系统最大的区别在于免费

B．Linux是单用户多任务的操作系统

C．Linux不是UNIX的变种，因此不能将Linux上的程序移植到UNIX主机上运行

D．Linux操作系统具有虚拟内存的能力，可以利用硬盘来扩展内存

答案

参考答案：D

解析： Linux操作系统与Windows NT、NetWare、UNIX等传统网络操作系统最大的区别在于它开放源代码，Linux支持多用户多任务，在同一时间内可以有多个用户使用主机，虽然它不是UNIX的变种，但符合UNIX标准，可以将Linux上的程序移植到UNIX主机上运行。

单项选择题

科学的建设程序应当在坚持（）的原则基础上，突出优化决策、竞争择优、委托监理的原则。

A先招标、后施工

B.先勘察、后设计、再工

C.科学决策

D竞争择优
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单项选择题

Even plants can run a fever, especially when they are under attack by insects or disease. But (1) humans, plants can have their temperature (2) from 3,000 feet away—straight up. A decade ago, (3) the infrared scanning technology developed for military purpose and other satellites, physicist Stephen Paley (4) a quick way to take the temperature of crops to determine (5) ones are under stress. The goal was to let farmer (6) target pesticide spraying (7) rain poison on a whole field, which (8) include plants that don’t have the pest problem.

Even better, Paley’s Remote Scanning Services Company could detect crop problem before they became (9) to the eye. Mounted on a plane flown at 3,000 feet (10) , an infrared scanner measured the heat emitted by crops. The data were (11) into a color-coded map showing (12) plants were running "fevers". Farmers could then spot spray, using 50 to 70 percent less pesticide than they (13) would.

The bad news is that Paley’s company closed down in 1984, after only three years. Farmers (14) the new technology and long-term backers were hard (15) . But with the renewed concern about pesticides on produce, and refinements in infrared scanning, Paley hopes to (16) into operation. Agriculture experts have no doubt about the technology works. "This technique can be used (17) 75 percent of agricultural land in the United States," says George Oerther of Texas A＆M. Ray Jackson, who recently retired from the Department of Agriculture, thinks (18) infrared crop scanning could be adopted by the end of the decade. But (19) Paley finds the financial backing (20) he failed to obtain 10 years ago.

7（）

A. more than

B. less than

C. rather than

D. other than
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