Final answer:
Submitting competitive bids to the client is not commonly required by codes of ethics for engineers.
Step-by-step explanation:
C) submitting competitive bids to the client is not commonly required by codes of ethics for engineers. Codes of ethics for engineers typically focus on principles such as acting as a faithful agent or trustee for the client, accepting payment for services only from the client, and spelling out all known conditions of bids and proposals. Submitting competitive bids is more commonly required in business practices rather than engineering ethics.