Final answer:
The best example of state-centric politics and who can have a voice is NATO and its member states, as it is a political alliance where sovereign states play a pivotal role in shaping policies and decisions.
Step-by-step explanation:
A good example of state-centric politics and who can have a voice is D) The North Atlantic Treaty Organization (NATO) and member states' participation. NATO represents a political alliance between Western European countries, Canada, and the United States, which reflects the interests and participation of its member states in security and defense matters. The structure of NATO allows for state-centric politics to play a crucial role, where the sovereignty and individual voices of each member country are pivotal in decision-making processes. In contrast to other options which include diverse actors (like NGO's or local communities), NATO's functioning is primarily state-focused, with member states holding the power to influence policies and actions at an international level.