Read the following text. Choose the best word(s) for each numbered blank and mark A, B, C or D on the ANSWER SHEET. (10 points)
　  Happy people work differently. They’re more productive, more creative, and willing to take greater risks. And new research suggests that happiness might influence 　1　 firms work, too.
　  Companies located in places with happier people invest more, according to a recent research paper. 　2　, firms in happy places spend more on R&D (research and development). That’s because happiness is linked to the kind of longer-term thinking 　3　 for making investments for the future.
　  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 activity of publicly traded firms in those areas.
　  　7　 enough, firms’ investment and R&D intensity were correlated with the happiness of the area in which they were 　8　. But is it really happiness that’s linked to investment, or could something else about happier cities 　9　 why firms there spend more on R&D? To find out, the researchers controlled for various 　10　 that might make firms more likely to invest—like size, industry, and sales—and for indicators that a place was 　11　 to live in, like growth in wages or population. The link between happiness and investment generally 　12　 even after accounting for these things.
　  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 happiness inequality.
　  　17　 this doesn’t prove that happiness causes firms to invest more or to take a longer-term view, the authors believe it 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&D more than the average,” said one researcher. ______ 

A.sufficient

B.famous

C.perfect

D.necessary