- Mountains can cause the water in the air mass to condense
- Mountain is a kind of geographic obstacles
- Hence, mountain is the geographic obstacle that can cause the water in the air mass to condense

Hence, mountain is the geographic obstacle that can cause the water in the air mass to condense
Question
What geographic obstacle causes water to condense in an air mass as the air mass moves?

Context
- Mountains can cause the water in the air mass to condense 
- Mountain is a kind of geographic obstacles