Answer:
D. Several factors led to the beginning of World War I.
Step-by-step 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.