Question

the best example of cause and effect after the congress of vienna is
napoleon was defeated, so france started a revolution.
austria won territory in italy, so italy adopted austrian customs.
spain became a monarchy, so the french empire was weakened.
the french empire was demolished, so liberal ideology grew.

Explanation:

After the Congress of Vienna, the French Empire was demolished. This led to the growth of liberal ideology as the old order was disrupted and new ideas could spread. Napoleon's defeat did not directly cause a French revolution after the Congress of Vienna. Austria winning territory in Italy did not mean Italy adopted Austrian customs in a direct cause - effect as described. Spain becoming a monarchy was not the cause of the French Empire's weakening in the context of the Congress of Vienna.

Answer:

the French empire was demolished, so liberal ideology grew.