Why did the fighting go on after the armistice was signed

No one could possibly know when the armistice was to be signed, or what hour be fixed for the cessation of hostilities so that the only thing for us to do, and which I did as commander in chief of the American forces, and which Marshal Foch did as commander in chief of the Allied armies was to continue the military activities  

The answer is in the first line Hope this help

people can eat food during that time

answer; (d) i believe that the correct answer is americans finally ran out of ammunition;