"The library is very quiet."
I know that その can be used as "the" but even without it the sentence means the same thing.
No. Sono is never 'the' duolingo has many huge problems with their new Japanese program and this is one of them. Japanese does not have articles EXCEPT demonstrative articles. If you don't remember highschool English...those are 'this that and that over there'. Sono means 'that' and that is ALL that it means when it isn't in an expression.
No, その means the in the sense that it is referring to something talked about in the previous conversation. It doesn't need to be physically near to the speaker and the listener.
If you go through the English course for Japanese speakers every "the" translates to その so it does not relate to the beta.
Funny though.. Duo doesnt seem consistant with sono = the. Personally, this is the first place i have heard sono mean anything but 'that'. So it messes me up a whole lot.
I know I cant expect much from a free program but the level of proof reading or consistency for a language program is disappointing, and confusing beginning learners. I believe most would agree that using Genki or Minna no nihongo would provide a better learning outcome