Answer:
The correct answer is a. variable cost changes with production activity and fixed cost remains constant.
Explanation:
The fixed cost is constant and does not changes with the output level. It remains constant through out the production process. fixed costs are those expenses which are paid independent of activity. So it is not affected by quantity of production.
While on the other hand variable cost is the cost of raw materials and other inputs. So, it changes with the level of production.