For the proximity factor, the matching description is: "You interact easily with a person who is readily available and in the same environment as yours".
It's been proven that repeated exposure to a certain stimuli is enough to influence attraction towards it. Even when there's not a lot to gain from that particular stimuli, the mere fact that the interaction with it is easy and convenient, will prompt attraction.
For the familiarity factor, the matching description is: "You tend to get attracted to people with whom you frequently talk".
The more time we spend interacting with somebody, the more shared interests and traits we'll find between us and them. A feeling of familiarity will grow around these interactions and this means safety. The more we know about someone through conversation, the more likely we are to stick with them because we'll more easily read and predict their behavior in the future.
Finally, for the reciprocity factor, the matching description is: "You are attracted towards people who like you". Research strongly suggests that being liked by someone is one of the biggest reasons that makes us like them back. Being likable makes us feel good about ourselves, so we're attracted to people that reflect our likability.
I hope this is clear and helpful to you!