The city code for Juneau, Alaska is JNU. This code is assigned by the International Air Transport Association (IATA) and is used by airlines and travel agencies to identify airports in a standardized manner. Juneau, being the capital city of Alaska, has its unique IATA code that helps facilitate travel arrangements and flight bookings specifically to and from that location.
The other codes pertain to different cities, which is why they do not apply to Juneau. For instance, ANC refers to Anchorage, while SEA is the code for Seattle. KDN is not an IATA code for any major airport in Alaska and therefore does not correspond to Juneau either. Thus, JNU accurately represents Juneau, making it the correct choice.