In the Experiment That Observes How People Become Less Prone

In the experiment that observes how people become less prone to violate a local ordinance on littering, the factor that changed their behavior was, predominantly:

A) the imposition of a strong financial disincentives.
B) the warnings issued by law enforcement about their activities.
C) a raising of public conscience about the effects of littering.
D) the potential benefits of littering.