Which is a popular argument among the defenders of the U$.$S$.$ health system?

a$.$ Administrative costs are too high because of the government involvement in healthcare.

b$.$ Costs of healthcare could be reduced significantly by shifting to a government$-$financed single$-$payer system.

c$.$ Private insurance companies should receive tax break in order to reduce their costs and ultimately the premiums they charge.

d$.$ The international differences observed in health data reflect differing approaches to diet and exercise.