"Soup is tasty food."
Translation:Zupa to smaczne jedzenie.
Zupa to smaczne jedzenie - is the only possible selection of words from the new 'clicking on offered words' question format. The words Zupa jest smacznym jedzeniem are not included.
Well, it's fine as long as you can create one of the starred answers, and you say you can.
I see why you'd ask that, but forms like "smacznem" don't exist in contemporary Polish. I think this could be correct some centuries ago (not sure), but not nowadays.
That doesn't mean that in will work in every grammar construction, or even every sentence where it's shown in the hints. The hints are for the whole course.
Nevertheless, here you can answer with "Zupa to smaczne jedzenie" or "Zupa jest smacznym jedzeniem". See here for more info: https://forum.duolingo.com/comment/16373167