The correct answer is - D. It processed oil into fuel and rubber used in the war.
The petrochemical industry saw a huge development during the World War II. The reason for the rapid and very big development was that this industry was in charge to process the oil into fuel and rubber. Both the fuel and the rubber were heavily used during the war. The fuel was especially important because it was what was making the military vehicles run, and without it the military would have had tons of vehicles that were not going to be usable.