C. Several factors led to the beginning of World War I.
The topic sentence from the passage shows us that it follows a cause and effect pattern. It sets the reader up to understand that the rest of the passage will be about several factors that caused World War I. The rest of the options are the different factors that led to World War I. They do not use key words that would indicate a cause and effect patterns like the words "Several" and "led" do in the first sentence.