The correct answer is:
D. The country began prioritizing European refugees under the immigration quota system.
After World War II, U.S. immigration policy shifted to accommodate the large number of European refugees fleeing the devastation of the war. This included the 1948 Displaced Persons Act, which specifically aimed to help refugees from Europe. Although there were later changes to quotas and immigration practices, the immediate post-war period saw a focus on aiding European individuals in need.