Why isnt choice A correct here

Hello @izyat, You suggested that the answer to this supply-side question requires something "concrete." I take that to mean that you are looking for an economically viable answer to this question. However, the author is only using an "economic metaphor" (Line 8.) The author equates the immigrants' cultural characteristics with the supply-side. Cultural characteristics may be intangible, but the author spends half the passage discussing them, so we cannot ignore them. Pay attention to this part of the question stem: "as such elements are explained in the passage." We don't need a strong understanding of economics to answer this question. We just need to follow the author's reasoning. The question asks us for a supply-side element of the labor market, which the author has already described as cultural characteristics. Only one of the answer choices fits this description, and that is C.