Government-subsidized healthcare services can create a free-rider problem in the healthcare market because ______.
 a. people would cancel private insurance policies and use government-subsidized coverage when they are sick
 b. when hospitals receive payment from a government-subsidized program, the hospital has less incentive to carry out medical research
 c. the supply of healthcare would increase
 d. when hospitals receive payment from a government-subsidized program, the hospital is less efficient