Final answer:
According to the proximity principle in social psychology, Kareem is most likely to become friends with Jordan, his next-door neighbor at Fuller Apartments, as regular contact significantly increases the likelihood of friendship formation.
Step-by-step explanation:
A significant body of research points to proximity as the most influential factor in forming friendships and relationships. Considering the details provided, Kareem, after moving into Fuller Apartments, is most likely to become friends with someone he sees often and has more contact with. Among the individuals mentioned, Jordan, Kareem's next-door neighbor at Fuller, is the person with whom Kareem is most likely to form a friendship according to the proximity principle.
Regular interactions foster a greater opportunity for a relationship to develop, making Jordan an ideal candidate for friendship. This principle is supported by the research referencing the fact that people are more likely to become friends with those who live in close proximity, such as in the same dorm, apartment building, or neighborhood.