I've been testing discussed translations in Google translate lately just to compare. It translated this French sentence to, "The key is yellow office." hahaha
However, if you change "du" to "de" .. it then translates it to, "The office key is yellow."
There is obviously a discrepancy somewhere here. It seems this sentence is unnatural even in French.
This sentence is quite natural in French. If you want to know if something sounds natural, please don't rely on a machine translator to guide you. One can play on Google Translate until the English seems perfect, but it is an illusion to think that the language in which you aren't fluent (be it French or any another) looks just as good.
Bottom line: Google Translate cannot think. You need a human for that.
i wrote, "the bureau key is yellow" and it's marked wrong. Seems to me like the word can be translated as either. If duolingo is going to mark me wrong, it would at least be nice to give me an explanation why.