A、About 25%. B、About 15%. C、About 20%. D、About 50%. C选项的内容表明，本题考查百分比，听音时应留意相关的信息。短文中提到，研究发现每五个美国成年人中就有一个人吸烟，由此可推断，美国大约有20％的成年人吸烟

States with a highly educated populace and higher taxes on cigarettes have fewer smokers, according to a new Gallup study of poll data.
    The study found that one out of five American adults smoke, a number that has held relatively steady in recent years. Utah had the fewest smokers, at just 13 percent, while Kentucky and West Virginia tied for first place at 31 percent.
    The South and Midwest dominated in smoker-heavy states. Besides Kentucky and West Virginia, Tennessee, Indiana, Arkansas, Missouri, Ohio, Louisiana, South Carolina and Alabama all had populations in which 25 percent or more people smoked. States that were under the national smoking average of 21 percent included: California, Idaho, Montana, the District of Columbia, New Jersey, Minnesota, Hawaii, Massachusetts, Arizona and Maryland.
    Higher rates of smoking correlated with lower rates of formal education, according to the Gallup organisation. West Virginia, Kentucky, Arkansas, Indiana, Tennessee and Oklahoma, for example, are all states where fewer than 25 percent of residents have college degrees. Massachusetts, Connecticut, Maryland, New Jersey and the District of Columbia, all areas with high rates of education, had some of the lowest rates of smoking.
    Cigarette taxes are also associated with low smoking rates, though it’s not clear whether taxes discourage smoking or whether states with fewer smokers are more likely to pass high cigarette taxes. In states where smoking was well above average, the average state cigarette tax was $0.66 a pack. In average states, it was $1.59, and in below-average states, it was $2.02. States that discourage smoking with regulations against smoking in public places also had lower smoking rates.
Questions 19 to 21 are based on the passage you have just heard.
19. What percentage of American adults smoke, according to the study?
20. Which of the following states in America had the lowest smoking rate, according to the study?
21. What can be inferred from the passage?