It's necessary ____ the high－tech industry to lure international manufacturers to the city.A.to exploitB. ofexploitingC.to be exploitedD.for exploiting

_____
　　A.important
　　B.possible
　　C.close
　　D.necessary

Happy people work differently.They’re more productive,more creative,and willing to take greater risks.And new researchsuggeststhathappinessmightinfluence__1__firm’swork,too.Companies located in places with happier people invest more,according to a recent research paper.__2__,firms in happyplacesspend more on R&D（researchand development）.That’s becausehappiness is linked to the kind of longer-term thinking__3__formakinginvestmentsforthefuture.The researchers wanted to know if the__4__and inclination for risk-taking that come with happiness would__5__the way companies invested.So they compared U.S.cities’average happiness__6__by Gallup polling with the investment activityofpubliclytradedfirmsinthoseareas.__7__enough,firms’investment and R&D intensity were correlated with the happiness of the area in which they were__8__.Butisitreallyhappinessthat’slinkedtoinvestment,orcouldsomethingelseabouthappiercities__9__whyfirms there spend more on R&D?To find out,the researchers controlled for various__10__that might make firms more likely to invest–likesize,industry,andsales–andforindicatorsthataplacewas__11__tolivein,likegrowthinwagesorpopulation.Thelinkbetweenhappinessandinvestmentgenerally__12__evenafteraccountingforthesethings.The correlation between happiness and investment was particularly strong for younger firms,which the authors__13__to“less codified decision making process”and the possible presence of“younger and less__14__managers who are more likely to be influenced by sentiment.”The relationship was__15__stronger in places where happiness was spread more__16__.Firms seem to invest more in places where most people are relatively happy,rather than in places with happinessinequality.__17__thisdoesn’tprovethathappinesscausesfirmstoinvestmoreortotakealonger-termview,theauthorsbelieveit at least__18__at that possibility.It’s not hard to imagine that local culture and sentiment would help__19__how executives think about the future.“It surely seems plausible that happy people would be more forward-thinking and creative and__20__R&Dmorethantheaverage,”saidoneresearcher.3选？

A.sufficient
B.famous
C.perfect
D.necessary