Under the Employee Retirement Income Security Act, which of the following individuals or entities could be held liable as a fiduciary
a. Calamity Mutual, an insurance company that maintains custody of the assets of its clients' plans
b. Mercy General, a hospital that provides medical services to a corporation's employees
c. Suzy Cue, a payroll clerk who processes employees' time cards to ensure they are paid properly for work-related injuries
d. Prof. Karen Burton, a college professor who teaches a financial planning course