Final answer:
The units of the federal bureaucracy can be categorized by function performed, clientele served, and the source of their personnel, but not by the activities regulated. Option D is correct.
Step-by-step explanation:
The correct option that would NOT be considered a way to categorize the units that make up the federal bureaucracy is by the activities regulated. Categorizing the units by function performed refers to grouping them based on the specific tasks they carry out, such as defense, healthcare, or education. Categorizing by clientele served involves grouping units based on the specific groups of people they provide services to, such as veterans, children, or the elderly. Categorizing by the source of their personnel involves grouping units based on where their employees come from, such as hiring from within the government or recruiting from the private sector.