19 Which of the following policies is most consistent with the predictions of the Gravity Model of trade? (A) Encouraging domestic firms to increase research and development spending in order to reduce average production costs. (B) Reducing cross-border transportation and transaction costs through regional economic integration. (C) Requiring all firms to export goods while prohibiting them from importing products in the same category. (D) Dividing the domestic market into more administrative regions in order to increase product variety.