Language School Teacher: Although conventional wisdom holds that older adults struggle to learn new languages, several studies show that adults who have relocated to a city where their second language is the primary one in use are much more likely to have achieved true fluency in that second language. So it isn’t the case that our ability to learn a second language diminishes as we age; rather, the older we get, the more likely it is that we are tied to a specific location and can’t easily pick up and move to a new city to learn a second language.

Which of the following is an assumption on which the teacher’s argument depends?