Health Care Costs Rose More Than 10 Percent in 2011

Health care costs rose more than 10 percent in 2011, according to a survey of insurers by Aon Consulting Worldwide. If the increase in costs solely comes from increased prices for MRI and X-ray machines, then for the health care industry

A) fixed costs are increasing.
B) long run average total cost is decreasing.
C) productivity is increasing.
D) variable costs are increasing.