During which years did World War II take place?

World War II took place from 1939 to 1945, marking a significant era in global history characterized by widespread conflict involving many nations across the world. This war was precipitated by a variety of factors, including unresolved issues from World War I and the rise of totalitarian regimes. It involved major military engagements across Europe, Asia, Africa, and the Pacific, ultimately resulting in profound political, social, and economic changes worldwide. The years 1939 and 1945 signify the official start and end of the war, respectively, with the invasion of Poland by Germany being commonly recognized as the event that triggered the conflict, and the dropping of atomic bombs on Hiroshima and Nagasaki representing its conclusion.

The other options indicate significant events or periods in history but do not correspond to the timeline of World War II. For instance, the years 1914-1918 refer to World War I, while 1945-1950 includes the immediate post-war period and the beginnings of the Cold War. Lastly, 1929-1939 reflects the period of the Great Depression leading up to World War II but does not represent the war years themselves.