Which communication method involves reporting activities using a standardized format?

The correct choice is related to the standardized format used in military communications, particularly within NATO operations. The NATO report format is specifically designed for the effective and efficient reporting of information, allowing personnel to convey critical data consistently and clearly across different units and branches. This standardization helps ensure that all involved parties have a mutual understanding of the information being relayed, which is crucial in high-stakes environments like military operations.

In contrast, options such as informal briefings do not adhere to a structured format and can vary significantly in content and style, making them less effective for standardized reporting. The operational command structure, while essential in defining roles and responsibilities within military operations, does not pertain directly to the formatting of reports. Direct messaging protocols are more about the method of communication rather than the standardized reporting format itself. Therefore, the NATO report format stands out as the correct answer, as it embodies the principles of structured and effective communication in reporting activities.