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When 17-year-old Quattro Musser hangs out with friends, they don't drink beer or cruise around in cars with their dates. _____, they stick to G-rated activities such as rock- climbing or talking about books.

They are in good company, according to a new study showing that teenagers are increasingly delaying activities that had long been seen as rites of passage into _____. The study, published Tuesday in the journal Child Development, found that the percentage of adolescents in the U. S. who have a driver's license, who have tried alcohol, who date, and who work for pay has plummeted since 1976, with the most precipitous (急剧的) _____ in the past decade. The declines appeared across race, geographic, and socioeconomic lines, and in rural, urban, and suburban areas.

To be sure, more than half of teens still engage in these activities, but the _____ have slimmed considerably. Teens have also reported a steady decline in sexual activity in recent decades, as the portion of high school students who have had sex fell from 54 percent in 1991 to 41 percent in 2015, according to Centers for Disease Control statistics. ^u People say, 'Oh, it's because teenagers are more responsible, or more lazy, or more boring, ' but they're _____ the larger trend," said Jean Twenge, lead author of the study, which drew on seven large time-lag surveys of Americans. Rather, she said, kids may be less _____ in activities such as dating, driving or getting jobs because in today's society, they no longer need to.

According to an evolutionary psychology theory that a person's "life strategy" slows down or speeds up depending on his or her _____, exposure to a "harsh and unpredictable" environment leads to faster development, while a more resource-rich and secure environment has the _____ effect, the study said. In the first _____, "You'd have a lot of kids and be in survival mode, start having kids young, expect your kids will have kids young, and expect that there will be more _____and fewer resources, " said Twenge, a psychology professor at San Diego State University who is the author of "iGen： Why Today's Super- Connected Kids Are Growing Up Less Rebellious, More Tolerant, Less Happy-and Completely Unprepared for Adulthood."

In that model a teenage boy might be thinking more _____ about marriage, and driving a car and working for pay would be important for “ establishing mate value based on procurement of resources," the study said. But America is shifting more toward the _____model, and the change is apparent across the socioeconomic spectrum, Twenge said. ^uEven in families whose parents didn't have a college education. . . families are smaller, and the idea that children need to be carefully   _____ has really sunk in. ‘‘ The _____of ⁴¹ adult activities'' could not be attributed to more homework or extracurricular activities, the study said, noting that teens today spend fewer hours on homework and the same amount of time on extracurriculars as they did in the 1990 s (with the exception of community service, which has risen slightly). Nor could the use of smartphones and the Internet be entirely the _____, the report said, since the decline began before they were widely available. If the delay is to make room for creative exploration and forming better social and emotional connections, it is a good thing, he said.