"It is just a matter of time."

Translation: To tylko kwestia czasu.

[mcpk]

'To jest tylko sprawa czasu' is suggested as a correct answer, but 'to tylko sprawa czasu' is marked incorrect - why is that?

[Jellei]

That looks like an oversight, however... we've agreed that 'sprawa czasu' is strangely unidiomatic, I really can't imagine hearing that. So I'm going to delete this answer.

[Fabi3848]

Why is "To tylko kwestia z czasu" wrong here? Is "z" just unnecessary? I still struggle to determine when to use the prepositions and when not

[Jellei]

Hmm... it's like saying "matter from time" I guess? English "of" (almost?) always just translates to Polish Genitive case and no preposition.