Question

what contribution did the soldiers at valley forge make to the american revolution?
they successfully spied on british troops.
they won an important christmas eve surprise attack against the british.
they wrote letters that convinced the french to ally with the americans.
they were the main force that defeated the british.

Explanation:

The soldiers at Valley Forge were trained and became a more disciplined and effective fighting force. They were the main force that defeated the British in later battles. Spying was not their main contribution. The Christmas Eve surprise attack (Battle of Trenton) was led by Washington but not directly related to Valley Forge training. Letters to convince the French were more related to diplomats like Franklin.

Answer:

They were the main force that defeated the British.