Concept:Marginal cost is the extra cost incurred when one additional unit of output is produced.
Explanation:Production of each extra unit changes the total cost of output.
This change in total cost is called marginal cost.
It is written as
MC=ΔQΔTC, where
ΔTC is the change in total cost and
ΔQ is the change in output, usually one unit.
Fixed costs do not change when output increases by one unit, so option C is not correct.
Options B and D do not correctly describe marginal cost.
Therefore, marginal cost is best described as the change in total cost of output.
Answer:A. change in total cost of output