Fifteen percent of US teenagers aged 12 to 17 who own mobile phones have received nude（裸体）or nearly nude images of someone they know, according to a survey released on Tuesday.
Only four percent of mobile phone-owning   1  in that age group have sent sexually suggestive pictures of themselves, a practice known as "sexting,"   2  the Pew Research Center’s Internet & American Life Project.
The Pew survey found that girls and boys were equally as likely to have sent a suggestive picture to   3 person and  4   teenagers were more likely to have engaged in "sexting."
Eight percent of 17-year-olds with mobile phones have sent a sexually provocative（刺激的） image  5   texting and 30 percent have  6    a nude or nearly nude image on their phone.
Only four percent of 12-year-olds have sent suggestive images of   7  .
Amanda Lenhart, a senior research specialist at Pew and the author of the report, said sexually suggestive images have become a   8   of "relationship currency" for teens.
"These images are    9  as a part of or instead of sexual activity, or as a way of starting or  10  a relationship with a significant other," she said. "And they are also passed  11   to friends for their entertainment value, as a joke or for   12  ."
"The desire for risk-taking and sexual exploration during the teenage years   13   with a constant connection via mobile devices creates a 'perfect storm' for sexting," said Lenhart.
"Teenagers have always grappled with issues around sex and   14   , but their coming-of-age mistakes transgressions have never been so easily   15   and stored for others to see," she added.
The survey found that teens with unlimited text messaging plans were more likely to receive "sexts"   16   images of people they know. About 75 percent of mobile phone owning teens have unlimited plans.
Among this group, Pew said 18 percent reporting receiving "sexts"    17   with eight percent of teens on    18   data plans and three percent of teens who pay per message.
According to Pew, 58 percent of 12-year-olds own a mobile phone and 83 percent teens aged 17   19    .
Pew noted that a number of US states are grappling with how to  20   "sexting" among minors and some legislatures(立法机关) have stepped in to consider laws that would downgrade charges from felonies（重罪） to misdemeanors（轻罪）.
Pew conducted telephone interviews with 800 teens aged 12 to 17 and their parents between June 26 and September 24.
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(   ) 8. A. habit                  B. system              C. method             D. form
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