The answer to this question is "Britain blockaded Germany."
The explanation to this answer is that from 1914 up to 1919 the Allies restricted the supply of goods to Germany, causing disease and starvation in Germany. The British Royal Navy was bigger, stronger and more powerful than the German Kaiserliche Marine.
So the correct order of all the events from the question is:
-Britain blockaded Germany.
-The stalemate broke.
-Germany was forced to retreat.
-The armistice was signed.