Passage Summary: We tried telling people exercise is good, but it didn't work. We told people smoking is bad, and that worked. So, we should tell people not exercising is bad to get them moving.

Conclusion: Switching the focus of exercise campaigns from positive health benefits to the dangers of inactivity would increase their success rate.

Reasoning: Anti-smoking campaigns were successful by focusing on dangers, whereas exercise campaigns focusing on benefits have failed.

Analysis: The argument relies on a classic comparison between two different behaviors: smoking and exercising. It assumes that the public's lack of response to exercise campaigns is due to the message's focus rather than some other difference between the two activities. To be a necessary assumption, the argument must believe that what worked for curbing a vice (smoking) will also work for encouraging a virtue (exercise). Look for an answer that bridges this gap by suggesting the negative focus was the actual cause of the smoking campaign's success.