"Welke bergketen is dit?"
Translation:Which mountain range is this?
The phrase "a mountain chain" exists in English - it's in the Oxford Compact Dictionary
This was also my first reaction - in this region we call it a mountain chain and I believe chain would be a translation of keten??
There is a difference between a mountain range and a mountain chain. However, such difference is not present in the Dutch language (as far as I am aware), so it is probably a missing translation. Did you also report it? :)
(I will add it, don't worry! :D )