Final answer:
If the war in autumn of 1918 did not end soon, a peace treaty was the likely outcome, due to the exhaustion of the German military and societal pressures, culminating in the armistice on November 11, 1918.
Step-by-step explanation:
In autumn of 1918, considering the exhaustion of the German military and the civil unrest in Germany, it seems likely that if the war did not end soon, a peace treaty would be signed (option a). Military leaders had requested an armistice in desperate need to end the war, indicative of a willingness to engage in peace negotiations rather than continuing hostilities. The Argonne offensive by over a million U.S. soldiers and subsequent successful counteroffensives by the Allies significantly weakened German lines, making Germany's military situation unsustainable. With the abdication of Kaiser Wilhelm II and the shift in political power in Germany, the groundwork for the armistice, which would come into effect on November 11, was laid, showing that a cessation of war was the likely outcome if it continued any longer.