Which of the following is a VARIABLE cost that rises and falls with the volume of construction work performed?

Explanation

Materials such as concrete and lumber are variable costs: the amount spent rises and falls directly with job volume, and each purchase is traceable to a specific job. The other three are classified as overhead because they are NOT chargeable to any single job. Note for practising contractors: a commercial general liability premium is typically rated on payroll or gross receipts and audited at the end of the policy year, so the amount you ultimately pay does move with volume — but it is still overhead for cost-classification purposes, because it cannot be assigned to one project. The exam tests the classification, not the rating method.