Hello. It’s one of the first words we learn as babies, yet it’s one of the last words we think to use as adults today. That’s unfortunate, because saying hello is more than just saying hello——it is recognition of another’s worth. How might the world change——how might we change——if we mastered this word? To find out, I spent one month saying hello to every person I met. Here’s what I’ve learned.
　　 It can boost (促进) productivity. In one of the few studies ever done on this subject, Allan All day, an assistant professor of special education at Oklahoma State University, had middle school teachers greet their students individually each morning. This exchange of greetings raised the kids’ productivity. School went from impersonal to personal, and that resulted in more class participation and better grades.
　　 Environments influence friendliness. One study found that people in the city were less likely to shake hands with a stranger than those in the countryside. My experience was similar. Whatever the reason, my urban hellos were answered far less often than my rural ones. Similarly, people in vacation spots were far friendlier than those hurrying work downtown.
　　 It’s a form of universal health insurance. It’s impossible to say hello without smiling. And smiling has been shown to lower blood pressure, relieve stress and boost happiness. Apparently, a smile creates a similar effect in the recipient (接受者).
So maybe we can make the world a better place by____________.  After a month of doing it, I feel lighter and I have a better sense of well-being.
What does the author say about the adults’ saying hello today?
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Which sentence in the text is the closest in meaning to the following one?
　　Teachers and students got friendlier so that the students became more active in learning and scored higher in tests.
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Fill in the blank in Paragraph 5 with proper words. (within 5 words)
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What are the three effects of smiling on health according to the text. (within 8 words)
Smiling can ___________________________________________________________