Translation:Angels and demons cannot eat potatoes.
Halo teman! Remember that without a context, more based in sacred texts or books, or perhaps related to traditional arts like shadow puppets or dance, I think it is difficult to perceive what the exercise is talking about. More information or some context is needed. If not, how can we know if the agents of this sentence can actually do something or not? How can we now if they are part of a wayang representation, or perhaps a Balinese dance, or something different from other place or country? Firstly, the context needs to be set or the religious corpus needs to be constructed. And Duolingo does not show these possibilities here. As far as I know, the sentence is formed like that to practice the grammar, neither more nor less.
Selamat belajar! :)
I'm with you! ... Though being an angel might have enough perks to outweigh the sacrifice ;) ... I mean... teleportation, levitation, ... seeing God!!! might make one forget to eat anyway... ;) (Not keen on swapping place with 'setan' though :p )
But I think it's not even too hard on them because they can still eat sweet potato :) because that's 'ubi', not 'kentang manis' ;)