"The house is under snow."
Translation:Ev kar altında.
Ah, maybe you're Russian! (I guessed from the ))) :D)
Think of it this way: if you can use это and it's logical, you can use the "ın".
Дом - под снегом. is what you would normally say. But would you ever say: дом - под этим снегом? ... That would need an extremely specific context, no? Like, there is some snow here, some snow there etc. And the house is under THIS SPECIFIC snow… in that case you could use "karın".
I'm probably not making it any easier now either, but… oh well I tried :D
I suggest adding this sort of example to this lesson's Tips and Notes.
Also, I'm from Portugal and in Portuguese the difference between "under snow" (debaixo de neve) and "under the snow" (debaixo da neve) is not apparent to most people. We could easily use the second option to mean all snow in general.