Answer:
Accountability
Step-by-step explanation:
A Fiduciary is an agent for a Principal/Client. The legal or special relationship of trust, confidence, or responsibility between two or more parties, most commonly a "Fiduciary" and a "Principal/Client", is called the Fiduciary Duty.
There are various fiduciary duties an agent owes a client, these duties include, honesty, confidentiality, loyalty, full disclosure, care and accountability.
The duty of accountability requires the agent to report to the principal promptly all money and property received and paid out, and upon request, to tender an account of these actions.
Hence the action of Mark is a breach of the fiduciary duty of Accountability.