How Can Liberal Theories of International Relations Be Distinguished from Realism

How can liberal theories of international relations be distinguished from realism?

A) Realism believes people learn from negative historical events,whereas liberalists believe they learn from positive ones.
B) Realism is less likely to believe in the unitary-actor assumption than liberal theories.
C) Realists see the rules of international relations as timeless and unchanging,whereas liberal theorists see the rules of international relations as evolving incrementally.
D) Realists favor absolute gains,whereas liberals favor relative gains.