Answer: D. Citizens of the United States
Explanation: The Bill of Rights is the first ten amendments to the United States Constitution. These amendments were added to protect the individual rights of U.S. citizens from the federal government. The Bill of Rights was written and adopted by the U.S. Congress, and it became part of the Constitution in 1791. It was not intended to apply to the citizens of any other country, such as Great Britain. Therefore, the target audience of the Bill of Rights is the citizens of the United States.