How does a long adjective become a pronoun ? Help asa

As with the short forms of su(s), long-form possessive adjectives and pronouns may be clarified in the third- person forms. For adjectives, the long form suyo/a(s) can be replaced by the construction de + pronoun in order to clarify the identity of the possessor. —Their host is arriving now.

Explanation:

if your asking for what that says, it is

which of these words is an

but i don't know what sentence your asking for the adjective from.