Which of the Following Most Accurately Describes a Fiduciary

Which of the following most accurately describes a fiduciary?

A) A fiduciary is hired by the stockholders to audit the accounts of the firm.
B) A fiduciary is contracted by law to be legally responsible for the firm.
C) A fiduciary is an agent who has custody over things of value to the principle and a responsibility to act in the best interests of the principle he or she represents.
D) A fiduciary is an agent hired by the firm's stockholders and is responsible for ensuring that the firm effectively controls its costs.