Answer:
The words from the excerpt that best support the official nature of the document are:
"authorize" and "impose"
Step-by-step explanation:
This official document is giving certain people permission and power. Notice that, throughout the text, we have several strong words, such as "authorize", "prescribe", "determine", and "impose". Those words help convey the sense of authority of the document and the people involved - those who have written it and those who are addressed by it. The same words, if used in an unofficial, regular document or text, would be considered rude, even arrogant. However, since this context does involve the delegation of power and authority, such words are acceptable and necessary.