A variable cost is a cost that.

A) varies per unit at every level of activity.
B) occurs at various times during the year.
C) various in total in proportion to changes in the level of activity.
D) may or may not be incurred, depending on management's discretion.

The correct answer is letter "C": varies in total in proportion to changes in the level of activity.

Explanation:

There are three types of costs a company can incur: fixed costs, variable costs, and mixed costs. Fixed costs are those whose total costs do not vary when the level of output changes. Variable costs change the total costs when the volume of production increases or decreases. Mixed costs are a combination of fixed and variable costs.

an online clothing brand

explanation: