Let's look at our options, starting with the last. Natural rights are rights that cannot be taken away, but they aren't in the Constitution (D is wrong). The Declaration of Independence is a totally different document from the Constitution (C is wrong). The Articles of Confederation are also, I think, a different document (B is wrong).
The Bill of Rights is the first ten amendments to the constitution that protects the rights of each person (or the individual). A is correct!
Answer: Bill of Rights