Final answer:
Variable overhead costs can experience both spending and efficiency variances as they increase or decrease with changes in output levels. They do not inherently have unused capacity and are subject to variances from standard expectations.
Step-by-step explanation:
The question concerns the nature of variable overhead costs in relation to production and efficiency. Variable costs, such as labor and raw materials, tend to increase or decrease with changes in output levels. Contrary to the possible options provided in the question, variable overhead costs indeed can have both a spending variance and an efficiency variance. A spending variance occurs when the actual cost of variable inputs differs from the standard cost expected for the actual level of output. An efficiency variance occurs when the quantity of variable inputs used is different from the amount expected for the actual level of output.
Therefore, the proper statement regarding variable overhead costs is that they do have the potential for both spending and efficiency variances, a key concept to understand within managerial accounting and cost control processes.
From the options given in this question, option B) Variable overhead costs have no production-volume variance could be considered true if the perspective taken is that variable overhead costs directly vary with the level of production and thus do not result in variances related directly to the volume of production, as they adjust accordingly.