Which statement reflects a rigid protocol mentioned in the memorandum?

The statement that reflects a rigid protocol mentioned in the memorandum emphasizes a strict action taken regarding the handling of mail. By stating that mail without bills will be sent back to the sender, it showcases a clear and unchangeable policy regarding mail processing. This indicates a definitive rule or standard operating procedure that must be followed, which is characteristic of a rigid protocol.

The focus on mail that lacks a specific component (bills) and the consequence of returning such mail directly aligns with the concept of adherence to a strict guideline, leaving no room for exception or interpretation. Other statements, while they may reflect processes, do not convey the same level of inflexibility or the enforcement of a specific consequence.