Which of the following describes a characteristic of variable costs?

Variable costs are expenses that change in direct proportion to the level of production or output. As production increases or decreases, these costs adjust accordingly. For example, if a company manufactures more goods, it will incur higher costs for materials, labor, and utilities that are directly tied to the production volume. Conversely, if production decreases, these costs will decline as well. This makes option B the most accurate description of variable costs.

In contrast, the first option refers to fixed costs, which remain constant regardless of the company's output level. The third option mistakenly suggests that variable costs can remain fixed over time, which is inconsistent with their nature of fluctuating based on production. Lastly, while marketing expenses can be variable, they are not exclusively classified as such, as they can also include fixed elements; hence, option D does not correctly define the essential characteristic of variable costs.