The sentence that shows correct capitalization is Mr. Brown always makes his students read both the Bill of Rights and the Constitution of the United States.
This is the correct option because the AP Stylebook states that the first letters of the names of bills, laws and amendments must always be capitalized. However, only content words that are part of the name of these documents should be capitalized. For that reason, the first option is incorrect: the "o" of "of" in "Bill of Rights" must not be capitalized. The second option is also incorrect because there is no capitalization of Bill of Rights or the Constitution. Furthermore, while in the last option Bill of Rights has been capitalized in a correct way, the "c" in the Constitution has not been capitalized. In that way, the third option is the only one that presents correct capitalization.