The hint said offen could mean loose, and that makes a lot more sense than open in this context. Why is it not right?
"Loose" really makes no sense here. The sentence means the ending is open to interpretation.
My dictionary agrees with you :), but Duolingo accepted this a moment ago: "With that the end remains open"
'Therefore' is the translation given but my answer is shown to be wrong and 'thereby'substituted!