Answer:
a. Alpharetta and Roswell are in the same housing market.
Step-by-step explanation:
Looking at the scenario all the people that look at houses in Alpharetta also look at houses in Roswell. People that look at houses in Roswell also look at houses in Alpharetta. Both of these categories do not look at houses in John's Creek. This presupposes that Alpharetta and Roswell are in the same housing market and John's Creek is not.
To reinforce this assumption people that purchase homes in Johns Creek look for homes only in Johns Creek.