The correct answer is: B. not stationary
A cost driver is a factor that causes a change in cost. The relationship between cost and cost drivers is not stationary because the cost of a product or service can change depending on the factors that are driving the cost. For example, the cost of manufacturing a product can change if the price of raw materials changes.
Option A is incorrect because the relationship between cost and cost drivers is not always stationary.
Option C is incorrect because the relationship between cost and cost drivers is not always intrinsic.
Option D is incorrect because the relationship between cost and cost drivers is not always extrinsic.