One reason for the German surrender in 1918 was that

Amany German soldiers were no longer willing to fight.
Bthe German tactic of trench warfare was a failure.
Cthe German submarine fleet had been destroyed.
Dthe German blockade of France had failed.

Verified Answer :

One reason for the German surrender in 1918 was that "a. many German soldiers were no longer willing to fight," since especially with the entrance of the US into the war it was becoming clear that the Allies would win. 

One reason for the German surrender in 1918 was that many German soldiers were no longer willing to fight.