What Has Been the Impetus for Using Alternatives to Incarceration

What has been the impetus for using alternatives to incarceration?

A) court rulings that indicate incarcerating certain offenders is unconstitutional
B) research findings that indicate incarceration increases an offender's likelihood of recidivism
C) a paradigmatic shift from retribution to rehabilitative ideals
D) prison overcrowding and the high cost of constructing new prisons