Which of the following represents a possession word correctly?

The word "anybody's" is the correct representation of a possession word because it indicates ownership or belonging. In this case, "anybody's" refers to something that belongs to anyone, showing that the item, quality, or characteristic is associated specifically with 'anybody.' This usage effectively conveys the concept of possession.

The other options do not function as possession words. "You're" is a contraction of "you are," which conveys a relationship or state rather than ownership. "Whose" can indicate possession, but it typically functions as an interrogative or relative pronoun, asking about or connecting possession rather than expressing it directly. "They're" is also a contraction, standing for "they are," which similarly does not convey ownership.