Final answer:
The propinquity effect suggests that people who work in the same building are most likely to become friends due to frequent contact.
Step-by-step explanation:
According to the propinquity effect, the likelihood of forming friendships increases with greater proximity—meaning individuals have more contact with each other.
This stems from the idea that regular contact provides the opportunity to get to know someone, making it easier to establish a relationship. Thus, the people most likely to become friends according to the propinquity effect are those who work in the same building, as they are in regular contact with one another, such as in an office environment or a shared workspace.