Welcome back to the 70s ladies and gents :)
Why is "the little green plate" wrong?
It's one of the included translations. In case that's what you typed in and got marked wrong, please send us a screenshot next time something similar happens.
Why is there a period after this? It isn't a complete sentence in English because there is no verb. Is this a complete sentence in Greek or can you put a period at the end of a phrase in Greek?
Why not, it could be an answer... I.g. "which one?" (would you like to buy or use, should I take...)