When on november 11th, 1918, an armistice was signed to end world war i, the war's biggest losers were because their governments ceased to exist.
a. the former industrial powers of britain and germany
b. russia, the u. s., and austria-hungary
c. russia, austria-hungary, and the ottoman empire
d. the prisoners of war

Austria-Hungary dissolved as a resuly of WW1; so it's a safe option.

D is definitely wrong: prisoners of War don't have governents.
A - neither do industrial powers, not really.
B is wrong because U.S. didn't cease to exist.

So this leaves us with C! C is correct, Ottoman empire colapsed after the war and Russia turned Soviet Union.