Which major war primarily between European powers, with the United States entering in 1917?

• A. World War II
• B. World War I
• C. Revolutionary War
• D. Cold War

Answer: (B)

The key idea is recognizing which conflict was mainly fought by European powers and when the United States joined. That description fits World War I: it began in 1914 with the major European empires and their alliances clashing across the continent, and the United States entered the war in 1917, tipping the balance with fresh troops and resources. The war continued until 1918, ending with the Treaty of Versailles in 1919, which reshaped Europe and beyond. In contrast, the other events don’t fit this pattern: World War II drew in many regions and the U.S. entered in 1941; the Revolutionary War happened in the 18th century between American colonies and Britain; and the Cold War was a long period of political tension rather than a single European-wide war.