Review the passage:
Richie loves to walk his friends' dogs at Lake Eola Park. For example,
Kim's Labrador retriever Murphy or Gary's bulldog Kembo.
Beautiful women, Richie has learned, gravitate toward
guys with cute dogs.
You chose the third part, Beautiful women, Richie has learned, gravitate toward guys with cute dogs. This part has a main clause: Women is the subject; gravitate is the verb. A fragment will not have a main clause.