Which of the Following Is Not a Principle of the Separate

Which of the following is not a principle of the separate confinement system?

A) Prisoners would not be treated vengefully but should be convinced that through hard and selective forms of suffering they could change their lives.
B) Solitary confinement would prevent further corruption inside prison.
C) Solitary confinement is expensive.
D) In isolation, offenders would reflect on their transgressions and repent.