The right answer is A: Allied bombing of Germany 1942 change the war because it helped pave the way for a later all-out offensive.
The so-called strategic bombing campaign, also known as "area bombing," which started in February 1942, was first aimed at directing systematic aerial attacks at civilian places, such as cities, with the goal of demoralizing and inflicting terror upon the German population that lived in them. Later on, it targeted railroads hubs, factories, and oil plants. This put a very significant strain on Germany, since it caused a great deal of destruction and limited its resources greatly - for instance, it could not produce enough aircraft or fuel.
These continuous and strategic attacks proved to be ultimately decisive in the Allied victory over Nazi Germany in 1945, since they progressively undermined the German war effort and paved the way for the succcesful offensive of the Allies.