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设A,B为满足AB=0的任意两个非零矩阵,则必有()
A.A的列向量组线性相关,B的行向量组线性相关
B.A的列向量组线性相关,B的列向量组线性相关
C.A的行向量组线性相关,B的行向量组线性相关
D.A的行向量组线性相关,B的列向量组线性相关

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In 1924 America's National Research Council sent two engineers to supervise a series of industrial experiments at a large telephone-parts factory called the Hawthorne Plant near Chicago.It hoped they would learn how stop-floor lighting 1 workers'productivity.Instead,the studies ended 2 giving their name to the"Hawthorne effect",the extremely influential idea that the very 3 to being experimented upon changed subjects'behavior.The idea arose because of the 4 behavior of the women in the Hawthorne plant.According to 5 of the experiments,their hourly output rose when lighting was increased,but also when it was dimmed.It did not 6 what was done in the experiment;7 something was changed,productivity rose.A(n)8 that they were being experimented upon seemed to be 9 to alter workers'behavior 10 itself.After several decades,the same data were 11 to econometric the analysis.Hawthorne experiments has another surprise store 12the descriptions on record,no systematic 13 was found that levels of productivity were related to changes in lighting.It turns out that peculiar way of conducting the experiments may be have let to 14 interpretation of what happed.15,lighting was always changed on a Sunday.When work started again on Monday,output 16 rose compared with the previous Saturday and 17 to rise for the next couple of days.18,a comparison with data for weeks when there was no experimentation showed that output always went up on Monday,workers 19 to be diligent for the first few days of the week in any case,before 20 a plateau and then slackening off.This suggests that the alleged"Hawthorne effect"is hard to pin down.3选?
A.truth
B.sight
C.act
D.proof
The music industry and You Tube are set to go head-to-head this week in a crucial vote in brussels that could force the digital giant to pay billions of dollars in fees to popular artists such as Taylor Swift Ed Sheeran and Katy Perry.For years the music industry has argued that You Tube exploits the lack of legal protection around music videos being viewed on its service to pay minimal amounts to artists and labels YouTube got a bloody nose in last months vote but its supporters are expected to gather the MEPs needed to challenge that decision and force a vote by all 751 members of the parliament Last month's vote was a fantastic result,but I'm sure there will be some push back.YouTube is the biggest music service,full stop,by some margin and has been a severe imbalance in what artists receive.It is righting a wrong really.said Martin Mills,founder of Beggars Group.Taylor Swift has led the fight for artists to get a better share of revenues in the age of the digital music giants.In 2014,she pulled her music from Spotify,saying artists receive a tiny royalty per song play and has been the catalyst for the much better deals struck by record labels with Spotify in the past 18 months“Despacito would probably not have become the global phenomenon it did without YouTube,”says Mark Mulligan,analyst at MIDiA Research.Last year,Luis Fonsi and daddy Yankee's reggaeton hit took the world by storm,becoming the most streamed song of all time You tube is the number one place where young people discover music.If you are going to create global hits you need You Tube and it is becoming more important to musicians."YouTube makes money from advertising and last year paid 856m(&650m)in royalties to music companies-an estimated 67 cents from each of its 1.3 billion music lovers annually.In the UK,record labels and artists earn more than double the royalties from the sale of 4.1m vinyl records than they did from the 25bn music videos watched on YouTube last year Musician Billy Bragg says the battle against You Tube is less about the potential financial windfall that artists might get,and more about making sure the new digital music power players play fair.We,ve all seen how,with the recent data protection legislation,the European Union has shifted power to the individual online,he says.u Now theyre seeking to do the same for artists.All were asking for is a level playing field.rebalancing the power between artists and the internet tech giants who are making massive profits while paying tiny royalties You Tube has made moves to mollify the industry,launching a premium subscription service-two days before the crucial European vote-a move Jean-Michel Jarre,electro-pioneer and president of music body Cisac,has cynically called"indirect lobbying"to try to improve its image
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A.It includes unreasonable provisions in the contract.
B.It pays music artists considerably less than its rival services.hune.es ariosto
C.It demands other digital giants to pay in full to artists.I.vs ns bed,snarls se borner
D.It exploits legal leaks to pay artists poorly for media sales
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Much exciting research is going on in an effort to find( )these questions.Foremost is the work of Jean Piaget,the Swiss psychologist who pioneered the field and whose theories have had an unparalleled impact on education,especially in Europe.
A.answers
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C.resolutions
D.conclusions
To finance the program they had to turn to the public( )the funds they needed.
for
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