A predicate in grammar is "the part of a sentence in which something is asserted or denied of the subject of a sentence" (Collins): it always includes a verb and possibly some objects. In "the bottles are his", "his" refers back to the subject (his bottles) and is "predicative"; in "he eats his", "his" doesn't refer back to "he", but to an omitted object (food?). In the first case in Italian you can omit the article (le bottiglie sono sue), in the second you can't (e.g. lui mangia il suo).
No; the adjective suo/sua/suoi/sue means both his and her. The gender and number, like with any adjective, must match the noun it refers to, so "le bottiglie" -> "le sue bottiglie" -> "le bottiglie sono le sue" or "le bottiglie sono sue". That could mean both "the bottles are hers" and "the bottles are his".
Can someone confirm if i'm right about this? I'm so confused and i feel like i'm not making sense of it.
Does "le sue" ever change in regards to "le bottiglie"? Like in the sentence "Susie, Betty, and Sarah collect trash. The bottles are theirs." Will that still be le sue because THEY are WOMEN, or does it switch to le loro? Or does it do neither, because it refers only to the bottles and not to the people who own them?
Since this is ambiguous and I know that possessives follow gender of object rather than possessor, I wrote his/hers. I think it should have counted since we aren't given context. Pronouns need antecedents and without them, I should be able to use both and still get the credit.