Q:"Hello"-it's one of the first words we learn as babies, yet it's one of the last ones we think to use as adults. That's regrettable , because saying hello is more than just saying hello-it is the respect of another's worth. How might the world change-how might we change-if we used this word well? To find out, l spent one month saying hello to every person I met. Here's what I've learned. It can improve productivity. In one of the few studies ever done on this subject, Allan Allday, 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 led to 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. And researchers say, pleasure environments generally encourage more smiles and hellos than unpleasant ones. My experience was similar. Whatever the reason, my hellos were answered far less often than the ones in the countryside. Similarly, people in vacation areas, like the Jersey Shore, were far friendlier than those hurrying to work in the centre of the city. It's a form of health insurance . It's impossible to say hello without smiling. And smiling has been shown to lower blood pressure , make people feel happier and improve happiness. It seems that saying hello creates a similar influence. So maybe we can make the world a better place by saying hello. After a month of doing it. I feel lighter and more connected and I have a better sense of _ . From the passage, we learn that _ . A) smiles can take the place of hellos B) people living in the city refuse to say hello C) environments play a role in creating friendliness D) having health insurance is more important than saying hello
A:
C