The difference between variable costs and fixed costs is (CMA adapted) A. Unit variable costs fluctuate and unit fixed costs remain constant. B. Unit variable costs are fixed over the relevant range and unit fixed costs are variable. C. Total variable costs are constant over the relevant range, while fixed costs change in the long-term. D. Total variable costs are variable over the relevant range but fixed in the long-term, while fixed costs never change.

(A) Unit variable costs fluctuate and unit fixed costs remain constant.

Explanation:

The fixed costs are the costs which have to be incurred always, irrespective of what the output produced is by the firm. For instance, a firm always has to charge depreciation on its fixed assets, pay salary to the premises staff and pay fixed salary to the managers for managing etc, irrespective of whatever output it produces.

Variable costs are the costs which vary with the level of output produced activity. For example, if more output is produced more will be the raw material payments, more will be the manufacturing related other expenses and more will be the wages paid to the labour etc and vice-versa.

Hence, thereby the per unit variable costs fluctuate and unit fixed costs remain constant.