Final answer:
An unreliable person is most likely to RSVP yes to a party but never show up, reflecting their tendency not to stick to their commitments.
Step-by-step explanation:
The question pertains to a personality trait associated with behavior regarding social events, specifically RSVPing and attendance. When considering who is most likely to RSVP yes to a party but never actually show up, the answer is b. Unreliable person. An unreliable person is someone who may not follow through on commitments, thus likely to say they will attend an event and then fail to do so, as opposed to a reliable individual, social butterfly, or considerate guest who would have different behavioral patterns regarding commitments.