There is literally no way to tell if this sentence is plural dative or singular accusative (because they are the same). Why you would put words without context into anything BUT the nominative is beyond me. If you do, it would be nice to at least indicate as much so that confusions like this do not happen.
I thought this would be "the complete names". How do you translate that then?
'Die vollständigen Namen'. The given sentence is written in the accusative, as indicated by 'den'. This is rather tricky without any context and might be overseen easily.
You're right. As you noted in your other comment, it's context-sensitive and I didn't notice this case.
I thought "den vollständigen Namen" would be plural dative. I thought singular accusative would be "den vollständigen Name".
Thanks! It would be very cool if Duolingo had a list of the cases for words like this under the hints... :)