Answer:
C. Vary in total in direct proportion to changes in the activity level.
Explanation:
Within a relevant angle, it is explained to vary in total in direct proportion to changes in the activity level.
Firstly, a variable cost is a corporate expense that changes in proportion to production output. Variable costs increase or decrease depending on a company's production volume; they rise as production increases and fall as production decreases.
A variable cost is a corporate expense that changes in proportion with production output.
Whether a firm makes sales or not, it must pay its fixed costs, as these costs are independent of output.