[单项选择]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
A. they are not expected to greatly enhance productivity
B. they do not lay the groundwork for the establishment of new jobs
C. the statistical data do not reflect the efficiency social media tools have brought
D. the statistical data do not show the expected cost in using social media tools