Option D is the answer.
Option A is rejected because in centralized communication notwork there is no free flow of communication in all directions ( all direction means between all the groups or layers of the network).
Option B is not the answer because centralized and decentralized networks has nothing to do with the size of organizations.
Option C is rejected because decision making process depends on the hard work and technical skills of groups of an organization about a field but not by the network discipline.
Option D is selected because in centralized network the information or decision making power is primarily limited to the upper level or higher members of organization and as mentioned decentralized decides on the basis of decision of all the groups or levels of the network.