The production possibilities frontiers depicted in the diagram to the right illustrate A. increases in both the labor force and capital stock. B. technological advances in both the tank and automobile industries. C. technological advances in the automobile industry, D. technological advances in the tank industry.

To determine the correct answer, we need to analyze the implications of the production possibilities frontier (PPF) in the context of the options provided. 1. **Understanding PPF**: The PPF illustrates the maximum possible output combinations of two goods (in this case, tanks and automobiles) that can be produced with available resources and technology. If the PPF shifts outward, it indicates an increase in production capacity, which can result from factors such as an increase in resources, technological advancements, or improvements in efficiency. 2. **Analyzing the Options**: - **A. increases in both the labor force and capital stock**: This would typically cause an outward shift in the PPF, but it does not specify which industry benefits from this increase. - **B. technological advances in both the tank and automobile industries**: This would also lead to an outward shift in the PPF, indicating that both goods can be produced more efficiently. - **C. technological advances in the automobile industry**: This would likely shift the PPF outward, but only for automobiles, not tanks. - **D. technological advances in the tank industry**: Similar to option C, this would shift the PPF outward for tanks only. 3. **Conclusion**: Without the diagram, we can infer that if the PPF is shifting outward, it could be due to technological advances in one or both industries. If the PPF is shifting outward for both goods, then option B is correct. If it is shifting outward for only one good, then options C or D would be correct. Given the context of the question, if the PPF is indeed showing an outward shift for both tanks and automobiles, the best answer would be: **B. technological advances in both the tank and automobile industries.** If the PPF is only shifting for one good, then the answer would depend on which good is being represented.