State governments are not sub-units of the federal government, but instead each is and does not report in any constitutional way to the federal government.

a. a confederacy
b. sovereign
c. dependent
d. an oligarchy

State governments are not sub-units of the federal government, but instead, each is B. sovereign and does not report in any constitutional way to the federal government. Sovereignty means having independent authority, and since the sentence describes state governments as not reporting to the federal government (and therefore being independent), the answer is B.