What more limited proposition on the idea

that more democracies correlates with less war has been proposed by Michael Doyle and derives from Kant and classical liberalism?
a. Liberal democracies only fight authoritarian regimes.
b. The more democracies in a system, the less propensity for war.
c. Liberal democracies do not fight other liberal democracies.
d. Liberal democracies only fight when clearly provoked or attacked.
e. Liberal democracies only fight when openly attacked or to protect vital resources.

Answer: c