Which phrase is an example of microeconomics? gross domestic product of the nation housing market in California rental market across the country cost of building supplies nationally

You have to assess the scale of both phrases. The gross domestic product of the nation housing market in California covers only one area. However, the second one has a much larger scale because the rental market is situated across the whole country.

Thus, if we are talking about microeconomics, the more appropriate phrase would be gross domestic product of the nation housing market in California.