When Skinner "Revisits" Walden II Years Later, Burris and Frazier

When Skinner "revisits" Walden II years later, Burris and Frazier appear to be their same old selves. What are the implications of their remaining much the same?

A) Skinner was not very creative as a writer.
B) Reinforcement should have made them different after a time.
C) This stability is not surprising due to the "protected" and invariable circumstances at Walden II.
D) In this show of invariance over time, Skinner provides testimony to the stability of personality.