阅读下列短文，然后根据短文的内容从每小题的四个选择项中选出最佳的一项。

     A woman heads into a popular New York City coffee shop on a cold winter morning. Just ahead of her, a man drops a few papers. The woman pauses to help gather them. A clerk at a busy store thanks a customer who has just bought something. "Enjoy," the young woman says, smiling widely. "Have a nice day." She sounds like she really means it. These are the common situations we may see every day.
     However, in her best-selling book Talk to the Hand, Lynne Truss argues that common good manners such as saying "Excuse me" almost no longer exist. There are certainly plenty who would agree with her. According to one recent study, 70 percent of the U. S. adults (成人) said people are ruder now than they were 20 years ago.
     Is it really true? We decided to find out if good manners are really hard to see. In this politeness study, reporters were sent to many cities in the world. They performed three experiments: "door tests" (would anyone hold the door open for them?); "paper drops" (who would help them gather a pile of "accidentally" dropped papers?); and "service tests" (which salesclerks would thank them for a purchase [购物]?)
     In New York, 60 tests (20 of each type) were done. Along the way, the reporters met all types of people: men and women of different races, ages, professions (职业), and income levels. And guess what? In the end, four out of every five people they met passed their politeness test—making New York the most polite city in the study.