Final answer:
Direct materials, direct labor, and sales commissions are all examples of variable costs that change with the level of production or sales.
Step-by-step explanation:
Among the options provided, all are examples of variable costs. Direct materials, direct labor, and sales commissions are costs that vary with the level of output or sales. These costs increase as more products are produced or sold. Direct materials are the raw inputs used in production that vary directly with the quantity produced. Direct labor is the cost of labor directly involved in the production process, which changes with the production volume. Sales commissions typically vary with the number of sales or the revenue generated.