"Lavoro sulla cucina."
In English, I am working 'on' any room means that you are renovating or redecorating, never just doing what you would usually do, such as cooking in the kitchen. That meaning would always use 'in'. I realize that this is probably tricky as far as translation goes, as the Italian word 'sul', as I understand it, means 'on', not 'in'. Could this Italian sentence mean both of those things, cooking and renovating, or does it only mean to work 'in' the kitchen?
This is confusing to the point of irritation! The correct answers appear to be both "I work on the kitchen" and "I work in the kitchen" as both of these are accepted and Duolingo Italian is now out of Beta. I prefer to keep my already prepositionally-challenged brain to thinking of "in" meaning, amongst other things, where someone is (apart from towns), and "su" meaning on. So, "I work on the kitchen" seems to make more sense in translation, even if most of us will have better things to do than mess about with kitchen installations, decorations, etc.