Which of the following would most likely cause a job to command a compensating wage differential?

a. There are barriers to the entry of new workers into the job market.
b. The job is more dangerous than most other occupations.
c. Wage rigidity prevents the wage rate from falling to the equilibrium level.
d. There has been an increase in the price of another input that is substitutable for labor.
e. The job market is dominated by one large firm.

B