Some of the vocabulary in thousand and one nights can be described as archaic because
a. it is commonly used today
b. it is language of the past
c. it is from another culture
d. it has unknown origins

Some of the vocabulary in Thousand and One Nights can be described as archaic because it is language of the past .

Archaic is defined as very old or old-fashioned; it also refers to a word or a style of language which is no longer used used but  is sometimes a resource to impart an old-fashioned flavour.

One Thousand and One Nights is a collection of Middle Eastern folk tales written in Arabic during the Islamic Golden Age.

the characters in string all have major secrets that they strive to avoid revealing throughout the play.