C is the answer to this question. The clue can be found in the name of the war. You can already tell that this lasted for a hundred years. The actual number of years that it lasted is 116 as it started in the year 1337 and ended in the year 1453. This war happened between England and France.
There were different conflicts that the two countries encountered. Each side has made sure to get more allies. This explains why this has lasted for a very long time. There were a lot of things that have happened to both countries that made them realize that the war is not good for them at all.