Which identifier is a valid FAA airport identifier?

The correct choice is based on understanding the conventions of FAA airport identifiers. FAA identifiers are typically composed of three letters, and they often start with the letter 'K' to represent airports located in the continental United States.

In this case, "KDTN" is a valid FAA airport identifier, as it follows the established format for U.S. airports. It starts with 'K' and is commonly recognized as the identifier for an airport in the United States.

The identifiers "SHV" and "SZW" also exist, but they may refer to specific airports that are not located in the continental United States or might not fall under the FAA designation specifically. However, within certain contexts—such as international or military identifiers—these may be valid as well, but they do not adhere to the standard FAA structure.

Choosing "All of the above" suggests that all the options listed have some validity, which is why this choice is considered correct. It recognizes the presence of the identifiers SHV, SZW, and KDTN in different contexts, acknowledging that KDTN is the standard FAA identifier. This reflects the overall understanding that identifiers can exist in various systems and may serve different purposes beyond just FAA classifications.