The concept of opportunity cost in a fully employed economy with technology and resources held constant tells us that a. output of all industries must contract until more resources are found. b. output cannot be increased in any industry. c. expansion of output in one industry means expansion cannot occur in another industry. d. expansion of output in one industry means output in another industry must contract.

In a fully employed economy, the idea of opportunity cost emphasizes the trade-offs inherent in the allocation of limited resources. When you choose to allocate more resources to one industry, you're sacrificing the potential output that could have been generated in another. This is akin to choosing between two delicious desserts; if you indulge in one, you must forgo the other, demonstrating that every decision has its costs. Think of it like a pizza party: if you decide to have a slice extra from one pizza, you're likely leaving less for other pizzas! So, choosing to ramp up production in one sector naturally means that resources (like labor, materials, etc.) have to be pulled from another area, leading to contraction there. This is why proper planning and resource management are crucial in an economy aiming for balanced growth.