I submitted 'orange tree' and it marked me wrong.
If it comes up again, use the report function.
I did. Thank you.
Reported as well. Oranges tree sounds weird in English.
I tried "A tree of oranges" and "the tree of oranges" as well as "orange tree" and all was marked wrong... Only "tree of oranges" without any article was accepted...:(
Of course, the most awkward translation possible.