B. ITS.
Each of the library books is placed in its correct location.
its refers to each of the library books.
A personal pronoun is a pronoun primarily associated with a particular grammatical person. It may refer to people, object, or animals.
The grammatical person may be first person, second person, or third person.
The personal pronoun "its" denotes the use of third person in a singular form.
Steinbeck is revealing the true plight of the workers which at that time was not widely discussed or frankly, cared about.
I think he's also trying to tell the reader that we should do what will affect the greater good instead of just reaping the benefits yourself.
Hope this helps!
~LENA~
