Which of the following would NOT be a violation of the linearity assumption?

1. You can smoke up to two cigarettes per day with no mortality effects, but after two cigarettes a day, it's really bad for you
2. Having a bachelors degree will boost your income a lot, but having a Ph.D. has almost no effect on your income after obtaining a Master's degree
3. More exercise is good for you until you pass a certain point, then more exercise is bad for you
4. Some people can drink 12 beers a day with no liver problems, but other people will drink 12 beers a day and die within a decade due to liver damage
5. All of the above would violate the linearity assumption