Suppose That You Want to Estimate How Health Insurance Affects

Suppose that you want to estimate how health insurance affects the mobility rate of workers.Which of the following is a problem with identifying this effect when you compare the mobility rate of those who have insurance with that of those who do not have insurance?

A) Jobs that offer health insurance tend to be the same in other ways (e.g.,pension plans or vacation) .
B) Jobs that offer health insurance may be better in other ways (e.g.,pension plans or vacation) .
C) Those with health insurance may not want to switch jobs because they are fearful of losing their insurance.
D) Health insurance does not affect worker mobility since workers are able to keep their insurance after changing jobs.