【单选题】

Through a combination of laws, education and cultural change, the struggle against drunk driving has come a long way since the 1970’s. This is one reason why traffic fatalities have been falling inAmerica to some 32,800 deaths in 2010, the lowest since the Truman administration. Other reasons include safer cars (with anti-lock brakes, air bags and such) and stricter seat-belt and speeding enforcement.

The counter trend has been increased distraction. Many things can compromise drivers’ attention, from kids to food or the radio.But mobile phones pose the biggest risk, for research shows that these gadgets distract in a more pernicious way.
The human brain has to work harder to process language and communication with somebody who is not physically present.Conversation with passengers is much less distracting, apparently because those passengers are also aware of the traffic situation and moderate their conversation. )
A、study byCarnegie Mellon University using brain imaging found that merely listening to somebody speak on the phone led to a 37% decrease in activity in the parietal lobe, where spatial tasks are processeD、This suggests that hands-free use of mobile phones cannot help much. Such distractions, according to one study, make drivers more collision-prone than having a blood-alcohol level of 0.08%, the legal limit inAmeric
A、It appears to raise the risk of an accident by four times. Texting multiplies the risk by several times again.
Officially, distraction accounted for 16% of traffic deaths in 2009 (up from 10% in 2005) and for 20% of injuries. The age group at greatest risk is, unsurprisingly, teenagers, though older drivers are not immune.But these statistics understate the truth, because few drivers after a crash admit to using mobiles, and police rarely demand phone records, says Joe Farrow, the head ofCalifornia’s Highway Patrol.
Laws vary widely. Japan in 1999 became the first country to ban hand-held mobile-phone use while driving, and most rich countries and many poor ones have since followeD、America is behind the trenD、 New York in 2001 became the first state with a similar law, and seven have since followeD、Thirty states have banned texting while driving.
But these laws are fiendishly difficult to enforce, says Mr Farrow. For instance, his officers must directly observe a driver texting (as opposed to just looking down) for several seconds to pull him over, which is not easy on a freeway. That said, highly visible enforcement makes a huge difference. Syracuse, New York, and Hartford,Connecticut, last year tried an experiment in which cops issued dramatically more citations for two weeks and mobile-phone use fell sharply in both places.
"I don’t think we’ll see an outright ban in my lifetime inCalifornia," says Joe Simitian, a state senator who has writtenCalifornia’s three laws against distracted driving. In a car-and-gadget culture, he reckons, the best hope is gradually to raise compliance over time, as with drunk driving. Technology might help—Google, for instance, is already testing cars that drive themselves and avoid accidents. In the meantime, says Ms. Smith, driving distracted must become, like drunk driving, "totally uncool, socially unacceptable", especially among teenagers.
All the following account for the falling of traffic fatalities inAmericaEXCEPT ______.
A、strict law enforcement
B．improvement of road conditions
C．struggle against drunk driving
D．safer car equipments