Is order important here? Can I say 나는 사흘 동안 케이크를 먹었어요?
I am also surprised by the order. It feels like cake should come closer to the verb? what are you doing for three days? eating cake. Can anyone clarify this?
I don't think it is. Korean has quite flexible word order. Both means the same, so this should be accepted, too. (reported)
@duolingo: where in the english sentence does it say 저는 can not be used???????????!!!!????
I thought we cannot use 나는 with 존댓말!!!
You can. You are higher but at the same time want to raise the listener.
The use of 삼일 is actually acceptable right? In the sense of everyday conversation use...
Yes, except there should be a space: 삼 일.
저는 사흘 동안 케이크를 먹었어요
There should be a space between 사흘 and 동안. I am disabling this exercise and we are sorry for the confusion.