Which of the following is not an example of a push factor that could encourage migration away from a place? a. the low cost of living in the southwestern united states b. the high unemployment rate in michigan due to the struggling auto industry c. the high cost of living in long island, ny d. the lack of affordable housing in the northeastern united states

Push factors are something that makes people want to move, pushes them out of the area so to speak. Pull factors would be things that attract them. 
So, (C) would also be a push factor because living costs are high, people may not be able to pay it so they'll move away. (D) is same, push factor, housing isn't affordable so people will want to move to somewhere cheaper. 
(B) and (A) on the other hand, are pull factors, good things attracting people. High employment, the better chance of getting a job, will attract people, and low living costs would attract people too as they can save money. 
Hope this helps :)