The ----- model for ethnic war, for example, includes factors reflecting incentive for collective action a) pattern b) structural c) model d) zeal

Let's complete the sentence.

The sentence describes a type of model for ethnic war that includes factors related to "incentive for collective action." This suggests an analysis of the underlying conditions or framework that drives such conflicts.

• a) pattern: While ethnic wars might have patterns, "pattern model" isn't a standard term for a theoretical framework in this context.
• b) structural: A structural model in social sciences refers to a model that examines the underlying structures, institutions, or conditions that influence phenomena. This fits well with analyzing "factors reflecting incentive for collective action" in ethnic war.
• c) model: This word is already used in the phrase "The ----- model," so using it again would be redundant and incorrect ("The model model").
• d) zeal: This refers to great energy or enthusiasm, which doesn't describe a type of model.

Therefore, the most appropriate word is b) structural.

The completed sentence is: The structural model for ethnic war, for example, includes factors reflecting incentive for collective action.