What Does the "Veil of Ignorance" Require Under Rawls's Distributive

What does the "veil of ignorance" require under Rawls's distributive justice theory?

A) Ethical obligations are decided by less intelligent members of society so that they can be understood by all.
B) Ethical obligations in society should not be made public,because if they were,individuals would strive to merely do the minimum.
C) Ethical obligations should be determined by persons who do not know their place in society.
D) Persons who have suffered an injustice should not be able to learn the identity of the person causing the injustice,at least when it is practical to keep this information from the person who was harmed.