Which topic is often used as a theme for studying world history since world was 1?

Did the roaring 20s have an impact on what was going to happen in World War 1? What does the new world mean? What was the first European nation to undertake large scale efforts at exploration and discovery? Why was the treaty of versallies called the treaty of versallies? Where did Hua Mulan lived? Where is Eurasia located? What is the study of tombs called? What do you call coureurs de bois mean in English? Did Albert Einstein become influenced by World War 2? What group did the ottomans join during world war 1? What world events of the early 20th century do you think led to the adoption of the Universal Declaration of Human Rights? Chivalry governed relation between who? How did organization of russia into republics help the bolsheviks gain and hold political control? What did a Weaver do in the 1600s? Who was the first chief of Air Staff of India? What region on the map below experienced a post-World War 2 communist revolution? What are the different kinds of dual sports? Who was able to vote in the 19th century in the US? William golding ia a native of what country? What was the name of the treaty that was signed at the end of World War 1?