题目

The U.S. Department of Labor statistics (统计) show that there is an oversupply of college-trained workers and that this oversupply is increasing. Already there have been more than enough teachers, engineers, physicists, aerospace experts, and other specialists. Yet colleges and graduate schools continue every year to turn out highly trained people to compete for jobs that aren't there. The result is that graduates cannot enter the professions for which they were trained and must take temporary jobs which do not require a college degree. On the other hand, there is a great need for skilled w若某多面体的三视图如图所示，则此多面体的体积是（  ）A．2B．4 C．6D．12