"What is that fox eating?"
Translation:Co žere ta liška?
The correct answer given was, "Co to ta liška žere?", contrary to the version shown here ("Co žere ta liška?"). Wouldn't "Co JE ta liška žere?" be correct as well?
I don't see where "to" comes from in the instance specified as correct back on the input screen.
No, there is certainly no "JE" in the Czech sentence. The "is" in the English sentence is an English specific part of the continuous form of the verb "is eating", it is really a part of it and you cannot translate it separately. "is eating" = "jí/žere" and also "eats"="jí/žere".
The "to" there is just a possible usage which sometimes accompanies "Co". Co děláš? (What are you doing?) is the same as Co to děláš? It just may help to make the sentence stronger. Also possible: Copak děláš? Copak to děláš?