The librarian in a local library wants to know the types of books children at his library prefer to read. He surveys every fourth child entering the library about the types of books they prefer to read. Of the 20 children surveyed, 6 children prefer science fiction, 9 children prefer mystery, and 5 children prefer non-fiction.

Identify the population in the situation above.
A.
all children who like to read
B.
all children entering the library
C.
every fourth child
D.
all children who prefer science fiction books