Which of the following is not one of the three branches of government?

The answer is D, as the Administrative branch is not considered one of the three primary branches of government. The structure of the United States government is defined by the separation of powers into three distinct branches: Legislative, Executive, and Judicial.

The Legislative branch is responsible for making laws and is composed of two chambers: the House of Representatives and the Senate. The Executive branch administers and enforces laws, led by the President, who also oversees the various federal agencies. The Judicial branch interprets laws and ensures they are applied fairly, consisting of the court system, including the Supreme Court.

Though there are administrative functions within the government, and various agencies and departments exist, these do not constitute a separate branch of government. Instead, they operate within the framework established by the three branches, focusing on implementing and managing specific functions related to governance.