Which of the Following Reasons Justifies the Increase in the Expenditure

Which of the following reasons justifies the increase in the expenditure on prescription drugs in the U.S.?

A) Lack of sufficient investment in research and development of new drugs
B) Proper functioning of the Medicare and Medicaid programs
C) Insufficient supply of prescription drugs leading to a shortage
D) Increasing returns to scale experienced by the drug manufacturers
E) Decrease in the time required to introduce a new drug into the market