Translation:The appetite comes while one is eating.
It said to translate "La the apetito venas dum oni manĝas." into English. So I wrote "The appetite comes whilst one is eating." Duolingo said that my answer was wrong, and told me the correct answer was "The appetite comes while one is eating."
The sentence is nonsensical in its English form, regardless whether one uses "while" or "whilst", but if Duolingo is going to allow "while" it should also allow "whilst".