I prefer cheese sandwiches to jam ones; Preferisco i panini al formaggio a quelli con la marmellata.
This sentence must have another way to translate it!! I tried "Preferisco i panini al formaggio a quelli di marmellata" ( I prefer cheese sandwiches to those of jam) which to me is easier to understand, but it wasn't correct. Can anyone explain why I am wrong? Thank you in advance!
Ciao, the preposition di in this type of sentence changes the meaning, so you must use it prudently:
Preferisco i panini al formaggio a quelli di marmellata.
means that the sandwich is not made of bread but of jam : ), because the preposition di also has a function of indicating to the material of which it is made something (complement of matter). Some examples:
La sedia di legno. (The wooden chair.)
Il tessuto di seta. (The silk fabric.)
In that case instead you are speaking only of topping (complement of quality):
Panino alla marmellata. that is Panino con la marmellata. ( Jam sandwich. - Sandwich with jam.).
However in other cases you can also/only use di:
Torta di mele or Torta alle mele, that is "made of apples (matter) VS with apples (quality)" (Apple cake)
Succo di frutta, that is "made of fruits", being a more generic indication (fruits, without any specification) usually "alla frutta" is not used (Fruit juice)
Succo di fragola or Succo alla fragola, that is "made of strawberry (matter) VS with strawberry (quality)" (Strawberry juice)
note: really, al = con in each case said, could also be a complement of manner or means, "something stuffed/made using x", it depends on your view.
Duolingo's sentence is correct.
Panino al formaggio means a sandwich with cheese. So the main ingredient is the bread and the cheese is either the flavour (→ panino al formaggio), or a secondary ingredient (→ panino col formaggio), both of which are common.
The same for a jam sandwich, which is either panino alla marmellata or con la marmellata.
The preposition di can only be used for referring to the main ingredient (e.g. zuppa di verdure).
The full explanation can be found here:
Thank you both for your explanations. Maybe it's the part of the sentence "those jam ones" which confuses me as it is not how I would say this. Sometimes I find the Duolingo English sentences stilted, I also have trouble with the use of "got" in a lot of sentences. I will certainly remember this now!