I think what is meant is "Clever people cross at the pedestrian crossing" but the translation accepted from the elements provided is nonsense to me. Who has ever even heard of a "crosswalk"?

Crosswalk is very american, I've never heard it called a pedestrian crossing -- I live in a city where no one uses them regardless of what you call them ughhh

De vigyázzatok! Budapesten a legtöbb autós nem áll meg a zebra előtt ha latja, hogy valaki át szeretne menni rajta. Mindig nézzetek kökrül, hogy jön-e autó, és átenged-e.

Never heard the word "crosswalk"

Crosswalk, zebra crossing and pedestrian crossing are all perfectly legitimate, depending on where you live - in U.K. or in the U.S., and they should all be accepted by Duolingo, but they are not.

Yes, I agree with the comment below. This is a Duolingo disaster. We never say crosswalk. I see that some Americans claim that they do but no-one would use this expression in the UK. If it's acceptable, I would strongly argue that the word "crossing" is equally so but it wasn't accepted.

I can't resist this and I'm guessing vvsey will know what's coming. In this instance, smart or clever is the characteristic much like intelligence. But what do we have here? "Az okos emberek etc..." In the example we had of intelligent people not jumping out of windows, there was no "Az" at the beginning. The distinction was between a quality possessed (i.e a characteristic) and the person or creature depicted (e.g a lion or a Hungarian politician) where "A" or "Az" would be essential. In view of the contrast between "Intelligens emberek etc...." and "Az okos emberek etc....." I'm left with the impression that the use of "A" or "Az" at the beginning in these instances is largely optional. If that's correct, I understand because many speech patterns are.

It is optional, but in fact usual, to use the article in general statements comprising a whole category of subjects - I believe there was a note to that effect under one of the lightbulbs.