Questionsare based on the following passage．
Millions of teenagers are in danger of putting their health at risk by getting hooked on ecigarettes，experts warn．Leading health researchers say they are "very concerned" by the growing number of youngsters trying the devices as a major new study reveals one in five teenagers has accessed them．E-cigarettes have been marketed as a healthier alternative to smoking conventional cigarettes．But previous research shows e-cigarettes generate poisonous chemicals similar to those found in tobacco and may harm the lungs and immune system．Worryingly， researchers at Liverpool John Moores University discovered 16% of teenagers who haveused e-cigarettes had never previously smoked．The experts also found e-cigarettes were "stronglyrelated" to drinking among teenagers．Study author Prof．Mark Bellis warned that such "rapid penetration into teenage culture of what is essentially a new drug-use option is without precedent （先例）．" He added: "Our research suggests that we should be very concerned about teenagers accessinge-cigarettes．While debate on e-cigarettes has focused largely on whether or not they act as a gateway to
tobacco cigarette use， e-cigarettes themselves contain a highly addictive （上瘾的） drug that may have more serious and longer lasting impacts on children because their brains are still developing．"Researchers surveyed 16，000 students aged 14 to 17 in the North "West of England and asked them about their alcohol and tobacco use．They found that one in five answered yes to the question: "Have you ever bought or tried electronic cigarettes？" More males than females said they had， and the figure increased with age and if they lived in a deprived poor area．
Of the teenagers that had accessed e-cigarettes，16% had never smoked，23% had tried smoking but did not like it，36% were regular smokers，12% only smoked when drinking， and 14% were ex-smokers．The research， published in journal BMC Public Health， also found teenagers who drank alcohol were significantly more likely to have accessed e-cigarettes than non-drinkers．
Among those who had never smoked， it was found that those who regularly have excessive drinking were four times more likely to access e-cigarettes than those who never drink．In all of those that drink，regardless of smoking status， e-cigarette access was associated with excessive drinking and involvement with violence after drinking．The researchers said their fmdings suggest that teenagers who usee-cigarettes are most susceptible （意受影响的） to other forms of substance use and risk-taking behaviour．
How have e-cigarettes been promoted in the market？ 查看材料

As a device meeting the physical and mental needs of smokers．
B. As a product preventing smokers from using tobacco products．
C. As a much healthier substitute for traditional cigarettes．
D. As a new device promoted among youngsters．