"Where is the metal?"
Translation:Wo ist das Metall?
Oh wow -- that is a bizarre sentence.
My first instinct would be to report it as "Sentence is unnatural or has an error", but I doubt that will be noticed, since it's too vague.
So perhaps deliberately submit an "answer" along the lines of "This sentence is unusual and should be removed from the course" and when you get marked wrong, report it as "my translation should be accepted".
Such suggested additional translations are visible to the course contributors and if they happen to look into the reports for that particular sentence, they may hopefully do something about it.
Given the number of reports (literally hundreds of thousands), it might take three or four years before it's noticed, but I can't think of anything better.
There are a number of weird sentences on the course that I think should really be dropped, but I don't know how to contact the course maintainers to make them aware of them more efficiently.