Final answer:
Between 1871 and 1921, the Treaty of Versailles and the Treaty of Brest-Litovsk were signed, while the Treaty of Ghent and the Treaty of Washington were signed outside this period.
Step-by-step explanation:
The period from 1871 to 1921 saw significant geopolitical changes and the signing of several major treaties. Among the options provided, the Treaty of Versailles and the Treaty of Brest-Litovsk fall within this timeframe. The Treaty of Ghent was signed earlier in December 1814, ending the War of 1812 between the United States and Great Britain. Similarly, the Treaty of Washington does not fit within the specified timeframe as it relates to a series of treaties, including one in 1871 which resolved various issues between the United States and Great Britain.
The Treaty of Versailles was one of the most significant treaties of the 20th century and concluded World War I. It was signed on June 28, 1919, between the Allies and Germany. On the other hand, the Treaty of Brest-Litovsk was an agreement signed on March 3, 1918, between the Bolshevik government of Russia and the Central Powers, marking Russia's exit from World War I.
The Washington Naval Conference of 1921-1922 took place after 1921 and resulted in the Four Power Treaty, among others, which focused on naval disarmament and the prevention of further territorial expansion in Asia by signatories. However, it does not directly fit within the specified timeframe for the question.