[单项选择]

The average young American now spends practically every waking minute—except for the time in school, though reluctantly—using a smart phone, computer, television or other electronic devices, according to a new study.
Those ages 8 to 18 spend seven and a half hours a day with such devices, compared with less than six and a half hours five years ago. And that does not count the hour and a half that youths spend texting, or the half hour they talk on their cellphones. And because so many of them are multitasking—say, surfing the Internet while listening to music—they pack on average nearly 11 hours of media content into that seven and a half hours.
The study’s findings shocked its authors, who had concluded in 2005 that use could not possibly grow further, and confirmed the fears of many parents whose children are constantly tethered to media devices. ^① It found, moreover, that heavy media use is associated with several negati
A. prevailing 
B. obvious 
C. notorious 
D. disastrous

The average young American now spends practically every waking minute—except for the time in school, though reluctantly—using a smart phone, computer, television or other electronic devices, according to a new study.
Those ages 8 to 18 spend seven and a half hours a day with such devices, compared with less than six and a half hours five years ago. And that does not count the hour and a half that youths spend texting, or the half hour they talk on their cellphones. And because so many of them are multitasking—say, surfing the Internet while listening to music—they pack on average nearly 11 hours of media content into that seven and a half hours.
The study’s findings shocked its authors, who had concluded in 2005 that use could not possibly grow further, and confirmed the fears of many parents whose children are constantly tethered to media devices. ^① It found, moreover, that heavy media use is associated with several negati
A. are not allowed to use electronic devices in school.
B. prefer a smart phone to a computer or television.
C. want to buy the newest electronic devices.
D. are all very good at sending texting.