Which of the following are examples of the principal-agent problem?

a) Insurance companies aren't always fully aware of a patient's family history.

b) Patients are unfamiliar with their doctor's medical training.

c) Consumers trust that doctors are ordering only relevant procedures.

d) Patients with insurance eat unhealthier foods than those without insurance.

The correct answer to the given question is option c) Consumers trust that doctors are ordering only relevant procedures.

Among the given options, in the option c, the consumers are the principals and the doctors are agents because the consumers are paying a fee to the doctors and are entrusting doctors to take decisions regarding their health. However, the doctors may negligently or deliberately order irrelevant procedures for making more making which might have bad consequences on the health of consumers. Thus, it is a case of principal-agent problem.

The option d is a case of moral hazard as the patients start eating unhealthier foods once they are given protection by the insurance companies. The option a is a case of adverse selection as the insurance companies aren't always fully aware of a patient's family history before giving protection to them. Thus, both these cases are examples of information asymmetry.