Lequel vs quel
On thoughtco.com I found this sentence
De tous vos matches, quel fut le plus difficile ? > Of all the matches you've played, which (one) was the most difficult / which was the most difficult one ?
Why isn't lequel used here? Usually, "which one" is translated as lequel. What's the rule? Is it because of passé simple here, or is it the register or...?
I'm not native in either language but I think:
"Quel(s)/Quelle(s) = What (m. and f.)"
Used when you ask for an answer that is in a broad group of possible answers that can be undefined:
"Quelle est ta voiture préféré ? - C'est l'Audi"
"Lequel/Laquelle/Lesquels/Lesquelles = Which (m. and f.)/ Which ones (m. and f.)
Used when you have a defined set of answers:
"Laquelle de ces trois voitures es le tienne ? - Celui à gauche"
To my knowledge, quelle/quel can definitely be translated as 'which'. Because, even if you implicitly know you are talking about a group of, say, three cars and you're asking about one of those three, you won't say "laquelle voiture a-t-elle", you'd say either "quelle voiture a-t-elle" or "laquelle a-t-elle".
Here is a thoughtco article on this topic, the one from which I took the sentence in the original post: https://www.thoughtco.com/french-interrogative-adjectives-1368795
Yeah, it depends wheter it's asking about a countable smaller amount of options of cheesse (in which case you use "which") or it's asking about any cheesse from a broader spectrum of cheesses (in which case you use "what"). In French is asking "Quel" and not "Lesquels" so I think the former would be the case.