设A为3阶可逆矩阵，将A的第2行加到第l行得8，再将B的第l列的（-1)倍加

____

根据以下资料，回答下列各题： In 1910．Henry Van Dyke wrote a book called The Spimt of America，which opened with this sentenee：“The Spirit of America is best known in Europe by one of its qualities—energy．”This has always been true．Americans have always been known for thelr mamc dvnamism．Some condemned this ambition as a scrambling after money.Others saw it in loftier terms．But energy has always been the country’s saving feature. So Americans should be especially alert to signs that the country is becoming less vital and assiduous．One of those signs comes to us from the labor market. According to figures from the Organization for Economic Cooperation and Development，the United States has a smailer share of prime age men in the work force than any other G-7 nation. Part of the problem has to do with human capital．More American men lack the emotional and professional skills they would need to contribute．According to data from the Bureau of Labor Statistics，35 percent of those without a high school diploma are out of the labor force．compared with less than lo percent of those with a college degree．Part of the Droblem has to do with structural changes in the economy．Sectors like government，health care and high．tech have been growing，generating jobs for collegegrads. Sectors like manufacturing，agriculture and energy have been getting more productive，but they have not been generating more jobs．Instead，companies are using machines or foreign workers. The resuIt is this：There are probably more idle men now than at any time slnce the Great Depression. and this time the problem is mostly structural，not cyclical．This is a big Droblem．It can’t be addressed through the sort of short—term Keynesian stimulus some on the left are still fantasizing about．It can’t be solved by simply reducing the size of government，as some on the right imagine． It will．probably require a broad menu of policies attacking the problem all at once： expanding community colleges and online learning；changing the corporate tax code and labor market rules to stimulate investment；adopting German-style. labor market practices like apprenticeship programs，wage subsidies and programs that extend benefits to the unemployed for six months as they start small businesses． Reinvigorating the missing fifth--bringing them back into the labor market and using their capabilities-will certainly require money．If this were a smart country．we’d be having a debate about how to shift money from programs that provide comfort and toward programs that spark reinvigoration． But，of course，that’S not what is happening．Discretionary spending，which might be used to instigate dynamism，is declining．Health care spending，which mostly provides comfort to those beyond working years，is expanding．Attempts to take money from health care to open it up for other uses are being crushed．We’re locking in the nation’S wealth into the Medicare program and closing off any possibility that we might do something significant to reinvigorate the missing fifth．Next time you see a politician demagoguing Medicare，ask this：Should we be using our resources in the manner of a nation in decline or one still committed to stoking the energy of its people and continuing its rise？ The loss of American dynamism concerned by the author is mainly manifested in the fact that_______．
A.American young are more indolent than their counterparts in other countries
B.America suffered from a higher rate of unemployment than other countries
C.More American young are out of work than their counterparts in other countries
D.American young are obssessed with the incessant quest for material comforts

The word“exonerate”is most closely in meaning to______．
A.confess the guilt
B.prove the innocence
C.execute the death
D.postpone the execution

A.off
B.on
C.down
D.forward

In the author’s opinion，the real situation of racial equality in America is_______．
A.pessimistic
B.optimistic
C.desperate
D.hopeful