How did Baron von Steuben contribute to the American Revolution?

A.He smuggled guns and gunpowder from Spain in order to supply the Continental Army.
B.He spied on the British troops and used the information he learned to prevent two battles.
C.He trained American soldiers and helped the Continental Army become better organized and more skilled.
D.He developed a secret code to help generals and other army leaders send messages to each other and their troops.