A、4,000. B、40,000. C、400,000. D、4,000,000. C录音提到在美国每年由于吸烟死亡的人数为40万，因此本题选C项。

Good morning. Today I’d like to talk about electronic cigarettes.[22]Electronic cigarettes are battery-operated devices designed to deliver nicotine with flavorings and other chemicals to users in vapor instead of smoke. They can be manufactured to resemble traditional tobacco cigarettes, cigars or pipes, or even everyday items like pens or USB memory sticks: newer devices, such as those with fillable tanks, may look different. More than 250 different e-cigarette brands are currently on the market. While e-cigarettes are often promoted as safer alternatives to traditional cigarettes, which deliver nicotine by burning tobacco, little is actually known yet about the health risks of using these devices.
    Cigarette smoking remains the leading preventable cause of sickness and mortality, responsible for over 400,000 deaths in the United States each year. E-cigarettes are designed to simulate the act of tobacco smoking by producing something that looks and feels like tobacco smoke and delivers nicotine but with less of the toxic chemicals produced by burning tobacco leaves.[24]Because they deliver nicotine without burning tobacco, e-cigarettes appear as if they may be a safer, less toxic alternative to conventional cigarettes. Although they do not produce tobacco smoke, e-cigarettes still contain nicotine and other potentially harmful chemicals. Nicotine is a highly addictive drug, and recent research suggests nicotine exposure may also prime the brain to become addicted to other substances. Also, testing of some e-cigarette products found the vapor to contain toxic chemicals. The health consequences of repeated exposure to these chemicals are not yet clear.
    Some people believe e-cigarette products may help smokers lower nicotine addiction while they are trying to discontinue their tobacco use. However, at this point it is unclear whether e-cigarettes may be effective as smoking-cessation aids. There is also the possibility that they could perpetuate the nicotine addiction and thus interfere with quitting.
    Because e-cigarettes are not currently marketed either as tobacco products or as devices having a therapeutic purpose, they are not regulated by the FDA In addition, there is currently no regulation of the liquids that are used in e-cigarettes. So, there are no accepted measures to confirm their purity or safety.
22. What do we learn about e-cigarettes?
23. How many deaths are caused by cigarette smoking in the US every year?
24. Why do e-cigarettes appear to be safer than conventional cigarettes?
25. Why are e-cigarettes not regulated by the FDA?