What Was the Significance of the Ruling in Johnson V

What was the significance of the ruling in Johnson v. Avery (1969) ?

A) The Court ruled it acceptable for inmates to help each other with legal work in case preparation.
B) The Court ruled that all correctional facilities housing medium to maximum security inmates must maintain access to a law library.
C) The Court determined that disciplinary proceedings differed from criminal prosecutions, such that prisoners were not owed the full due process rights to which a defendant on trial is entitled.
D) The Court ruled that inmates could sue the warden for depriving them of their constitutional rights under Section 1983.