Translation:This is a desk.
True. But 이것 그것 and 저것 are special compounds that denote this and that in English. So 이 집입니다 is incomprehensible. 이 집은 작습니다 works though.
Based on my own experience watching Korean shows, I know it means a desk/table. I didn't check the definition and went for "table" and got marked wrong. Smh.
Yeah, desk and table are very similar. But, in elementary Korean courses, desk is 책상 and table=탁자, and Koreans use them differently.
Well in English you wouldn't say "This is desk" so I'm guessing that's why?
Though that is probably the literal translation, because Korean doesn't have articles (the, a/an), I think Duo expects you to add them in when they are appropriate to write proper English sentences.