Columnist: Research shows significant reductions in the number of people smoking, and especially in the number of first-time smokers in those countries that have imposed stringent restrictions on tobacco advertising. This provides substantial grounds for disputing tobacco companies' claims that advertising has no significant causal impact on the tendency to smoke.
Which one of the following, if true, most undermines the columnist's reasoning?
People who smoke are unlikely to quit merely because they are no longer exposed to tobacco advertising.
In claiming that countries with stringent advertising laws see a decline in smoking, the author specifies that the decline is most prominent among first-time smokers. Even if current smokers usually don’t quit, limiting advertising still appears to deter would-be smokers, leaving the argument intact.
Broadcast media tend to have stricter restrictions on tobacco advertising than do print media.
We’re trying to weaken the author's claimed causal relationship between advertising laws and smoking rates, generally. Whether the degree of limitations can vary between media types doesn't affect that broader relationship, so this isn't useful.
Restrictions on tobacco advertising are imposed only in countries where a negative attitude toward tobacco use is already widespread and increasing.
This adds a third factor to the equation, one that affects both smoking rates and advertising laws. Now it looks like negative attitudes towards tobacco use are actually what cause a decline in smoking rates, as well as leading to stricter laws. By providing an alternative explanation for the correlation, this undermines the causal argument.
Weaken: Introduce or support an alternate explanation for a phenomenon.
Strengthen: Helps to eliminate an alternate explanation for a phenomenon.
Most people who begin smoking during adolescence continue to smoke throughout their lives.
This isn't strong enough to eliminate the potential impact of advertising laws, so it doesn't weaken. If 30 percent of smokers quit who otherwise wouldn't have, that's still significant, even if it's not "most." This also doesn't account for deterring first-time smokers.
People who are largely unaffected by tobacco advertising tend to be unaffected by other kinds of advertising as well.
We have no idea how many people are unaffected by tobacco advertising, and we're not concerned with advertising in general. This could be a weakener if almost all people were unaffected by tobacco advertising, but we don’t have that information.