Answer:
The correct answer is letter "C": varies in total in proportion to changes in the level of activity.
Step-by-step 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.