Question

Anyone familiar with One Flew Over the Cuckoo's Nest ?
Which of the following is a primary resource that would best enable a reader to understand the setting of One Flew Over the Cuckoo's Nest?
a. A 1980s documentary on life within 1950s mental institutions.
b. A research paper written on mental institutions in the 1880s.
c. A diary of a nurse in a mental institution during the 1950s.
d. None of the above is a primary resource.