An English reading question, please answer it, thank you

Answer C) Unrestricted immigration will undermine the American welfare state.

The question asks about the author’s views on U.S. immigration policy. Navigate to paragraph 6 based on the detail word “immigrant policy” In the last sentence, the author mentioned that immigration policy must consider the welfare system, "Anything we try to do as regards immigration laws has to be done in the context of a huge welfare state that is already a major, inescapable fact of life", combined with the previous sentence " "we do not have choice between the welfare state and open borders" (either preserving welfare or opening borders, you can't have your cake and eat it too), indicating that the author is worried that the continuous influx of immigrants will damage the welfare system, and the option "unrestrained immigration" corresponds to open borders.