The state is a network of exchanged benefits and beliefs, ______between rulers and citizens based on those laws and procedures that are______to the maintenance of community.

单项选择题The sheer diversity of tropical plants represents a seemingly______source of raw materials , of which only a few have been utilized.

单项选择题Documenting science s______philosophy would be______, since it is almost axiomatic that many philosophers use scientific concepts as the foundations for their speculations.