Which of the Following Would Be Considered Ex Post Facto

Which of the following would be considered ex post facto research?

A) A group of adults who live in close proximity to an airport is compared on their levels of stress to a matched group of adults from the same community who do not live near the airport, before and
After the expansion of the airport.
B) The levels of stress among the residents of a suburban community are measured and correlated to the distance of their homes from a local airport.
C) A sample of adults is recruited from the local community and assigned randomly to one of two conditions; half are asked to complete a series of self-report measures, including a measure of
Stress, while listening to white noise on a set of headphones and the other half are asked to
Complete the same measures while listening to a recording of airplane noise from a nearby airport.
D) Elementary school children and their parents are compared on a measure of stress given before and after the expansion of a nearby airport.