Final answer:
The cost that remains unchanged as output varies is the fixed cost, as it does not fluctuate with the level of production.
Step-by-step explanation:
The cost that does not change as output changes is fixed cost. Fixed costs are the expenditures that remain constant regardless of the level of production. An example of a fixed cost would be the rent paid on a factory or retail space; this cost stays the same no matter the quantity produced. On the other hand, variable costs, like labor and raw materials, fluctuate with the level of output. As more goods or services are produced, more workers or more work hours, as well as more raw materials, are required. Hence, variable costs adjust in accordance with the output level.