Option - a. is correct which states that there is both a central government and local governments including state governments.
Federal Government is a form of government in which the powers are divided between the central government and the local governments that are connected to one another through the central national government. In federal governments, some areas of public life are under the control of the Central Government and some areas of public life are under the control of local governments.
Reasons for other incorrect options:
Option - b. is incorrect because in federal principles of comity are formed for the political institutions to mutually recognize each other's legislative, executive, and judicial acts. The states do not have to follow these principles of comity but to reach mutual understandings with other political institutions through these principles.
Option - c. is incorrect because both central government and local state governments have sovereignty in some areas and share powers in other areas. Therefore, state governments cannot defer in all cases to the sovereign central government.
Option - d. is incorrect because all the states are not confederate to the central government and only the 11 unrecognized states are confederate states to the central government. Therefore, this option is incorrect.