"What is this camera?"
Translation:이 카메라는 무엇입니까?
Me too. You don't really need it if the context doesn't require it - if it is clear to the listener which camera you are speaking of. So if your friend is holding a camera, you wouldn't use 이, but if you were in a camera shop, you might point to a particular camera and then use 이. Duolingo is not giving us enough info to make that distinction in our answers ....