Even in the short run, a small business must set the price of a product at least equal to the _____ costs (per unit), or it must shut down

The answer is B) variable cost.

The variable costs for the business are raw material cost, labor cost, and variable overheads. In the short run, the fixed overheads are incurred irrespective of sale. The variable costs will move in direct proportion to sales volume, and if it's recovered by selling revenue, then the business should continue. In the short run, the business owner should set the selling price equal to variable cost.

In other options, fixed costs are not the variables considered in short-run decision making, and the selling revenue should be equal to total costs in long-run projections.