I accidentally typed "Jede" and it turns out that it is accepted as well. What is the difference between "Jeder" and "Jede" in this case and how do you know what gender of "Jede" to use?
'Jede' would refer to a feminine noun, like 'Jede Frau hat Eltern' (each woman has parents) but if you want to use it for 'each and every one' you normally use the male form. (what i mean to say is that the word parents doesn't have anything to do with it)
In daily use, "jeder" (the masculine form) is the correct form. You would only use "jede" if you were to imply a feministic background. For a while in the 90's, some people wrote "jede(r)" to make sure that absolutely nobody is offended.
I wrote "Alles haben Eltern", which was marked incorrect. One of the correct answers was "Alle haben Eltern". Why "Alle" and not "Alles"? I don't understand what was wrong about my answer.