Answer:
library books
Step-by-step explanation:
Remember that a research paper is an academic writing in which the author explores certain aspects of a determined topic, this must be based on evidence and already existing information developed by experts. It's purpose is to give an original view of the topic. Therefore the best source of information, in this case, are the library books. Library books have already been tested by other experts, this means the information presented is well supported, based on reality. The other sources are not suitable as the information obtained from them can be false or incorrect, it has not been developed using an specific method.