What Is the "Domino Theory" in the Context of the Cold

What is the "domino theory" in the context of the Cold War?

A) the hope that the establishment of markets for Western goods would lead to democratic reforms
B) the idea that Western Europe needed to present a united front against Communism, with each holding the other up
C) the fear that the fall of one country to Communism would result in the fall of others
D) the hope that the removal of key Soviet leaders would lead to the collapse of popular support for Communism
E) the observation that the violent repression of protestors almost always resulted in decreased support for the government in power