Bioscience:Secrets of the Sequence（1）
The warnings are everywhere — in newspaper and magazine articles， in televised public service announcements， even on cigarette packages — tobacco is harmful to your health. In fact， it can be and often is quite deadly. Notwithstanding， about three thousand Americans under eighteen take up smoking every day， and many of us are unable to stop. So， once we take that first or second puff， why do we become addicted?
- Added：2006
- Country：America
- Duration：30
- Time of update：2011/8/17 15:02:25