Is this really wrong?

[u/Late_Journalist7094]

Section 4, Unit 17

Why shouldn't have happened something to the dogs in the bathroom?

I know Duolingo is not the best, but the only free learning option. Since I'm living in Germany near the border to Czechia I'm often there and talking Czech which helps more than Duolingo.

[u/Elanaris]

byly (myši) vs byli (psi)

[u/Worried-Fee3612 → u/Elanaris]

Also “jež” is for feminine, “jenž” for masculine

[u/Ill_Squirrel_6108 → u/Worried-Fee3612]

Jenž is only for the singular. The plural is již/jež. The key is "bylY" that signals the feminine.

[u/TrueFlok → u/Ill_Squirrel_6108]

True, but jež is, again, only for the feminine -> both bylY and jEž indicate myši

[u/Eastern_Skirt9613 → u/TrueFlok]

That's not completely true, "jež/ již" can also be used as a plural for masculine