Non si sa implies the general public, "One does not know". It looks similar to reflexive verbs.
This also happens in Polish:
Nie wiadomo/Nie wie się
Why is 'has entered' wrong? :(
An impersonal construction in English can also be "you don't know" and that should be accepted.
But in italian, "you don't know" also means "tu non sai", so this is why it wasn't accepted
I see that Duolingo is engaged in current affairs such as refugees...
why can't it be "he doesn't know"?
i wrote "we don't know"
Non e saputo come la donna sia entrata in Italia
Questa frase non ha nessun senso credetemi
Sì, ce l'ha.