"Does this land belong to Terschelling or not?"
Translation:Behoort dit land tot Terschelling of niet?
I'm not really sure but from some quick googling and my gut feeling I get the impression you can use "behoren aan" for possession (Dit land behoort aan de koning - This land belongs to the king), and "behoren tot" for being part of something (De walvis behoort tot de zoogdieren - The whale belongs to the mammals). I've seen some examples where "bij" is used as well, but it sounds a bit strange to me (can't explain why). I would however say something like "Hoort dit land bij Terschelling?" instead of the sentence from this exercise ;)