It depends on which time period. But, probably A.
Explanation:
much of the knowledge written on them may have disappeared
Plessy v. Ferguson<span>, 163 U.S. 537 (1896), was a landmark decision of the U.S. Supreme Court issued in 1896. It upheld the constitutionality of racial segregation laws for public facilities as long as the segregated facilities were equal in quality – a doctrine that came to be known as "separate but equal".</span>
I think it's c but I am not sure
