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

a. 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

b. Having a bachelor's 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

c. More exercise is good for you, until you pass a certain point, then more exercise is bad for you

d. 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

e. All of the above would violate the linearity assumption

If we are using ordinary least squares as our estimation method, then we are pretty much assured of

a. Not having omitted variable bias

b. Having our residuals average 0 in expectation

c. Having a random sample

d. Having a linear relationship in the population data

e. None of the above are correct