"Carrie does not live in the mountains, unfortunately."
Translation:كَري لا تَسْكُن في ٱلْجَبَل لِلْأَسَف.
Yes it is, but in this case, they are talking about Carrie living in the mountains in general. They aren't talking about any specific mountains. In such a situation, Arabic would use the singular where English would use the plural. In the case of a city, both languages would use the singular. Every language has its idiomatic usages :-)