The two countries that lost the smallest percentage of their populations during World War I were Italy and the US.
Explanation:
1. Italy: Italy suffered less in terms of population loss during World War I compared to many other nations involved in the conflict. The impact on Italy's population was relatively smaller due to factors such as its late entry into the war and the majority of the fighting taking place in other regions.
2. US: The United States also experienced a relatively low percentage of population loss during World War I. The US joined the war effort later compared to European nations, and its direct involvement in terms of casualties was limited compared to countries that were engaged in prolonged and intense combat on their own soil.
Therefore, the correct answer to the question is Italy and the US as the two countries that lost the smallest percentage of their populations during World War I.
