The Allied victory in Europe was sealed after the allies beat the nazis at what final German offensive

The Battle of the Bulge, (16 December 1944 – 25 January 1945) was the last major German offensive campaign of World War II. It was launched through the densely forested Ardennes region of Wallonia in Belgium, France, and Luxembourg on the Western Front towards the end of World War II in the European theatre.

The Second Battle of Marne. (WW1) And  The Battle of The Bulge. (WW2)

Explanation:

I think it was the Battle of the Bulge. If you are talking about WW2.

i dont know but thats a great qusestion

i would say b. research typically uses a variety of sources