"The year seventeen twenty."
Translation:El año mil setecientos veinte.
I started with the correct answer but changed it to the incorrect answer suggested in the drop down clue. I thought they were trying to teach that we could use seventeen hundred for one thousand seven hundred as we can English. I probably should have been tipped off by the "mil" supplied in the sentence but I found the lesson more confusing than instructing. I still do not know if leaving one thousand (mil) out of the sentence would have made the translation correct.