The change in total cost per unit of change in output is known as by which name

Short Run Marginal Cost

The correct answer is Option (4) → Short Run Marginal Cost

The short run marginal cost (SMC) is defined as the change in total cost per unit of change in output.

SMC = Change in Total Cost/ Change in Output

It measures how much total cost increases when output increases by one unit in the short run, where some factors (like capital) are fixed.