Final answer:
The libraries of the World State contain only reference books to control the information available to citizens and maintain state power.
Step-by-step explanation:
The question asks why the libraries of the World State only contain reference books. The correct answer is: b) To control the information available to the citizens. This is done to ensure that only certain kinds of knowledge that align with the ideals and controls of the World State are available, thus preventing any form of subversion or dissent that might arise from access to a wider range of literature and historical texts. By controlling the information, the state can maintain its power and the status quo. Contrastingly, historical examples like the House of Wisdom in Baghdad or Enlightenment-era Europe show how access to a variety of books can foster learning and critical thought, which could be deemed dangerous in a controlled society.