What Is an Alternative to the Contagion Hypothesis for Why

What is an alternative to the contagion hypothesis for why civil wars tend to cluster regionally?

A) A rebellion in one country might inspire like-minded groups in neighboring states to engage in civil war.
B) Armed groups operating in one country might cross into a neighboring state and engage in violence there.
C) States finance domestic oppositions in their neighbors' territories.
D) Poor countries are likely to be located in similar regions of the world.
E) Civil wars cause refugees to spread across state boundaries and create conditions that facilitate the emergence of new civil wars.