已知x、y∈R,写出“x2+y2>2”的一个充分不必要条件:______.

题型:填空题

问题:

已知x、y∈R,写出“x2+y2>2”的一个充分不必要条件:______.

考点:充分条件与必要条件
题型:填空题

如果x2=4,那么x=______.

题型:填空题

PC机组成局域网时传输介质(俗称网线)选择很重要。常用的网线有双绞线、同轴电缆和 【20】 ,后者大多用于网络中的高速干线部分。

题型:填空题

In 1993, New York State ordered stores to charge a deposit on beverage (饮料) containers. Within a year, consumers had returned millions of aluminum cans and glass and plastic bottles. Plenty of companies were eager to accept the aluminum and glass as raw materials for new products, but because few could figure out what to do with the plastic, much of it wound up buried in landfills (垃圾填埋场). The problem was not limited to New York. Unfortunately, there were too few uses for second-hand plastic.

Today, one out of five plastic soda bottles is recycled (回收利用) in the United States. The reason for the change is that now there are dozens of companies across the country buying discarded plastic soda bottles and turning them into fence posts, paint brushes, etc.

As the New York experience shows, recycling involves more than simply separating valuable materials from the rest of the rubbish. A discard remains a discard until somebody figures out how to give it a second life—and until economic arrangements exist to give that second life value. Without adequate markets to absorb materials collected for recycling, throwaways actually depress prices for used materials.

Shrinking landfill space, and rising costs for burying and burning rubbish are forcing local governments to look more closely at recycling. In many areas, the East Coast especially, recycling is already the least expensive waste-management option. For every ton of waste recycled, a city avoids paying for its disposal, which, in parts of New York, amounts to savings of more than $100 per ton. Recycling also stimulates the local economy by creating jobs and trims the pollution control and energy costs of industries that make recycled products by giving them a more refined raw material.

The returned plastic bottles in New York used to ().

A. end up somewhere underground

B. be turned into raw materials

C. have a second-life value

D. be separated from other rubbish

题型:填空题

()的出笼标志的冷战的全面展开。

题型:填空题

Windows TAPI是微软公司Windows开放服务体系结构WOSA的一部分,有关它的说法不正确的是 ( )

A.它提供了一致的、设备无关机制

B.它管理PC和电话网络间所有的信号传送

C.通信应用程序不可通过TAPI接口访问调制解调器

D.它可以对共享的通信端口和设备进行仲裁

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