Which remark is appended to the report of a METAR or SPECI observation that is not transmitted?

In the context of METAR or SPECI observations, remarks that are not transmitted with the report typically fall under specific codes that denote their status. The remark "FIBI" indicates that the observation is an unreported flight information message and is not intended for transmission. This distinction is crucial for aviation weather reporting, as it helps differentiate between information that is relevant and can be disseminated versus information that remains internal or is used for further evaluation without being part of the official report.

The other options represent different types of remarks or codes that do not apply to unreported observations, which is why "FIBI" is the correct choice in this context. Each code serves a specific function within the reporting structure, emphasizing the importance of accurate terminology in weather observation documentation.