D. Several factors led to the beginning of World War I.
Explanation:
By starting the passage with this sentence, the author wants us to understand that the passage will use a cause and effect pattern. This is clear from the fact that the introductory sentence tells us that the passage will discuss the factors that led to WWI. This means that the events discussed are considered causes, while the war is considered an effect. The cause and effect structure is particularly useful when discussing historical events.
D. 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.
