划分各环境要素环境影响评价的工作等级，主要依据( )等因素。 A．提出预防或者减轻

贯彻“因地制宜”的方针，山区农业发展应侧重于

A．林业

B．种植业

C．畜牧业

D．机械化

强心甙中毒的停药指征是（）

A.频发室性早期

B.二联律

C.窦性心动过缓

D.视觉异常

E.呕心，呕吐

患者男性，25岁，因“突发头痛、呕吐、意识不清1小时”入院。既往身体健康，无高血压病史。查体：意识昏迷，格拉斯哥昏迷评分（GCS）8分，双侧瞳孔等大，对光反射灵敏。CT提示右侧额叶出血，量约40ml，中线结构左移。

该患者最可能的诊断是（）

A.动静脉畸形破裂出血

B.海绵状血管畸形出血

C.静脉畸形出血

D.淀粉样变性脑出血

E.动脉瘤出血

The economy may be troubled, but one area is thriving: social media. They begin with Facebook and extend through a dizzying array of companies that barely existed five years ago: Twitter, LinkedIn, Groupon, Yammer, Yelp, Flickr, Ning, Digg--and the list goes on. These companies are mostly private but have attracted the ardent attention of Wall Street and investors, with Facebook now worth a purported $ 75 billion and Groupon valued at close to $ 25 billion.
There can be little doubt that these companies enrich their founders as well as some investors. But do they add anything to overall economic activity While jobs in social media are growing fast, there were only about 21,000 listings last spring, a tiny fraction of the 150 million-member U. S. workforce. So do social-media tools enhance productivity or help us bridge the wealth divide Or are they simply social--entertaining and diverting us but a wash when it comes to national economic health
The answers are vital, because billions of dollars in investment capital are being spent on these ventures, and if we are to have a productive future economy, that capital needs to grow the economic pie~and not just among the elite of Silicon Valley and Wall Street. The U. S. retains a competitive advantage because of its ability to innovate, but if that innovation creates services that don’t turn into jobs, growth and prosperity, then it does us only marginal good.
The problem is that these tools are so new that it is extremely difficult to answer the questions definitively. As I was about to write this column, I overheard a ceil-phone conversation at an airport with this snippet.- "The company says they are using social media, but who knows if it is making any difference" Flash back nearly 20 years and the same question was being asked about the first Internet wave. Were Netscape and the Web enhancing our economy, or were people just spending more time at work checking out ESPN. com Official statistics weren’t designed to capture the benefits, and didn’t--until statistics mavens at the Federal Reserve, urged on by Alan Greenspan, refined the way they measured productivity. As a result of these somewhat controversial innovations, the late 1990s became a period of substantial technology-driven gains.
It is possible that the same gap exists today, that social-media tools are indeed laying the groundwork for new industries and jobs but aren’t yet registering on the statistical radar. Many companies believe social media make them more competitive. Ford and Zappos, for instance, use Twitter to market their products and address consumer complaints. Countless corporations have created internal Face-book pages and Yammer accounts for employees to communicate across divisions and regions. Industry groups for engineers, doctors and human-resources professionals have done the same to share new ideas and solutions on a constant basis rather than episodically at conferences. Staffing companies have been especially keen on social media; a senior executive at Manpower told me we should think of social-media tools as today’s version of the telephone. Yes, they are used for frivolity and all sorts of noneconomic activity (chatting with friends, passing the time), but they also help communication happen more efficiently.
One big question is what proportion of that benefit will be captured economically by consumers vs. corporations. Sure, social media allow people to compare prices and quality and assess which companies are good to work for and where jobs might be. They also may enhance education and idea sharing, but the caveat is that the people who use these tools are the ones with higher education and income to spend on technology, not the tens of millions whose position in today’s world has eroded so sharply. According to a recent Pew Foundation study, only 45% of adults making less than $ 30,000 have access to broadband, which is an essential component of using content-rich social media effectively.
And that is the tub. Like so many things these days, social media contribute to economic bifurcation. Dynamic companies are benefiting from these tools, even if the gains are tough to nail down in specific figures. Many individuals are benefiting too, using LinkedIn to find jobs and Groupon to find deals. But for now, the irony is that social media widen the social divide, making it even harder for the have-nots to navigate. They allow those with jobs to do them more effectively and companies that are profiting to profit more. But so far, they have done little to aid those who are being left behind. They are, in short, business as usual.

According to the passage, social media______.

A. have been existing for a number of decades
B. have been extending since 20 years ago
C. are contributing much to social and economic development
D. have emerged rapidly within the last decade